diff --git a/_examples/03_custom_resolver/federation/federation.pb.go b/_examples/03_custom_resolver/federation/federation.pb.go
index 399ed4f7..a12e1353 100644
--- a/_examples/03_custom_resolver/federation/federation.pb.go
+++ b/_examples/03_custom_resolver/federation/federation.pb.go
@@ -204,10 +204,11 @@ type PostV2Dev struct {
 	sizeCache     protoimpl.SizeCache
 	unknownFields protoimpl.UnknownFields
 
-	Id      string `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty"`
-	Title   string `protobuf:"bytes,2,opt,name=title,proto3" json:"title,omitempty"`
-	Content string `protobuf:"bytes,3,opt,name=content,proto3" json:"content,omitempty"`
-	User    *User  `protobuf:"bytes,4,opt,name=user,proto3" json:"user,omitempty"`
+	Id        string `protobuf:"bytes,1,opt,name=id,proto3" json:"id,omitempty"`
+	Title     string `protobuf:"bytes,2,opt,name=title,proto3" json:"title,omitempty"`
+	Content   string `protobuf:"bytes,3,opt,name=content,proto3" json:"content,omitempty"`
+	User      *User  `protobuf:"bytes,4,opt,name=user,proto3" json:"user,omitempty"`
+	NullCheck bool   `protobuf:"varint,5,opt,name=null_check,json=nullCheck,proto3" json:"null_check,omitempty"`
 }
 
 func (x *PostV2Dev) Reset() {
@@ -270,6 +271,13 @@ func (x *PostV2Dev) GetUser() *User {
 	return nil
 }
 
+func (x *PostV2Dev) GetNullCheck() bool {
+	if x != nil {
+		return x.NullCheck
+	}
+	return false
+}
+
 type User struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -419,6 +427,44 @@ func (x *ForNameless) GetBar() string {
 	return ""
 }
 
+type TypedNil struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+}
+
+func (x *TypedNil) Reset() {
+	*x = TypedNil{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_federation_federation_proto_msgTypes[6]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *TypedNil) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*TypedNil) ProtoMessage() {}
+
+func (x *TypedNil) ProtoReflect() protoreflect.Message {
+	mi := &file_federation_federation_proto_msgTypes[6]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use TypedNil.ProtoReflect.Descriptor instead.
+func (*TypedNil) Descriptor() ([]byte, []int) {
+	return file_federation_federation_proto_rawDescGZIP(), []int{6}
+}
+
 var File_federation_federation_proto protoreflect.FileDescriptor
 
 var file_federation_federation_proto_rawDesc = []byte{
@@ -463,7 +509,7 @@ var file_federation_federation_proto_rawDesc = []byte{
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@@ -471,7 +517,10 @@ var file_federation_federation_proto_rawDesc = []byte{
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+	0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x22, 0x00, 0x1a, 0x4e, 0x9a, 0x4a, 0x4b, 0x0a, 0x49, 0x0a,
+	0x0e, 0x0a, 0x01, 0x61, 0x12, 0x02, 0x08, 0x01, 0x1a, 0x05, 0x12, 0x03, 0x78, 0x78, 0x78, 0x0a,
+	0x10, 0x0a, 0x01, 0x62, 0x12, 0x04, 0x12, 0x02, 0x08, 0x03, 0x1a, 0x05, 0x0a, 0x03, 0x79, 0x79,
+	0x79, 0x0a, 0x18, 0x0a, 0x01, 0x63, 0x12, 0x0a, 0x1a, 0x08, 0x0a, 0x02, 0x08, 0x01, 0x12, 0x02,
+	0x08, 0x06, 0x1a, 0x07, 0x0a, 0x03, 0x7a, 0x7a, 0x7a, 0x18, 0x01, 0x0a, 0x0b, 0x0a, 0x01, 0x64,
+	0x12, 0x02, 0x08, 0x05, 0x1a, 0x02, 0x20, 0x01, 0x42, 0xcc, 0x01, 0x9a, 0x4a, 0x22, 0x12, 0x0f,
+	0x70, 0x6f, 0x73, 0x74, 0x2f, 0x70, 0x6f, 0x73, 0x74, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x12,
+	0x0f, 0x75, 0x73, 0x65, 0x72, 0x2f, 0x75, 0x73, 0x65, 0x72, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f,
+	0x0a, 0x14, 0x63, 0x6f, 0x6d, 0x2e, 0x66, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e,
+	0x2e, 0x76, 0x32, 0x64, 0x65, 0x76, 0x42, 0x0f, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69,
+	0x6f, 0x6e, 0x50, 0x72, 0x6f, 0x74, 0x6f, 0x50, 0x01, 0x5a, 0x1d, 0x65, 0x78, 0x61, 0x6d, 0x70,
+	0x6c, 0x65, 0x2f, 0x66, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3b, 0x66, 0x65,
+	0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0xa2, 0x02, 0x03, 0x46, 0x56, 0x58, 0xaa, 0x02,
+	0x10, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2e, 0x56, 0x32, 0x64, 0x65,
+	0x76, 0xca, 0x02, 0x10, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x5c, 0x56,
+	0x32, 0x64, 0x65, 0x76, 0xe2, 0x02, 0x1c, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f,
+	0x6e, 0x5c, 0x56, 0x32, 0x64, 0x65, 0x76, 0x5c, 0x47, 0x50, 0x42, 0x4d, 0x65, 0x74, 0x61, 0x64,
+	0x61, 0x74, 0x61, 0xea, 0x02, 0x11, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e,
+	0x3a, 0x3a, 0x56, 0x32, 0x64, 0x65, 0x76, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -538,7 +598,7 @@ func file_federation_federation_proto_rawDescGZIP() []byte {
 }
 
 var file_federation_federation_proto_enumTypes = make([]protoimpl.EnumInfo, 1)
-var file_federation_federation_proto_msgTypes = make([]protoimpl.MessageInfo, 6)
+var file_federation_federation_proto_msgTypes = make([]protoimpl.MessageInfo, 7)
 var file_federation_federation_proto_goTypes = []interface{}{
 	(PostV2DevType)(0),           // 0: federation.v2dev.PostV2devType
 	(*GetPostV2DevRequest)(nil),  // 1: federation.v2dev.GetPostV2devRequest
@@ -547,14 +607,15 @@ var file_federation_federation_proto_goTypes = []interface{}{
 	(*User)(nil),                 // 4: federation.v2dev.User
 	(*Unused)(nil),               // 5: federation.v2dev.Unused
 	(*ForNameless)(nil),          // 6: federation.v2dev.ForNameless
-	(*durationpb.Duration)(nil),  // 7: google.protobuf.Duration
-	(*Ref)(nil),                  // 8: federation.v2dev.Ref
+	(*TypedNil)(nil),             // 7: federation.v2dev.TypedNil
+	(*durationpb.Duration)(nil),  // 8: google.protobuf.Duration
+	(*Ref)(nil),                  // 9: federation.v2dev.Ref
 }
 var file_federation_federation_proto_depIdxs = []int32{
 	3, // 0: federation.v2dev.GetPostV2devResponse.post:type_name -> federation.v2dev.PostV2dev
 	0, // 1: federation.v2dev.GetPostV2devResponse.type:type_name -> federation.v2dev.PostV2devType
-	7, // 2: federation.v2dev.GetPostV2devResponse.env_c_value:type_name -> google.protobuf.Duration
-	8, // 3: federation.v2dev.GetPostV2devResponse.ref:type_name -> federation.v2dev.Ref
+	8, // 2: federation.v2dev.GetPostV2devResponse.env_c_value:type_name -> google.protobuf.Duration
+	9, // 3: federation.v2dev.GetPostV2devResponse.ref:type_name -> federation.v2dev.Ref
 	4, // 4: federation.v2dev.PostV2dev.user:type_name -> federation.v2dev.User
 	1, // 5: federation.v2dev.FederationV2devService.GetPostV2dev:input_type -> federation.v2dev.GetPostV2devRequest
 	2, // 6: federation.v2dev.FederationV2devService.GetPostV2dev:output_type -> federation.v2dev.GetPostV2devResponse
@@ -644,6 +705,18 @@ func file_federation_federation_proto_init() {
 				return nil
 			}
 		}
+		file_federation_federation_proto_msgTypes[6].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*TypedNil); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -651,7 +724,7 @@ func file_federation_federation_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_federation_federation_proto_rawDesc,
 			NumEnums:      1,
-			NumMessages:   6,
+			NumMessages:   7,
 			NumExtensions: 0,
 			NumServices:   1,
 		},
diff --git a/_examples/03_custom_resolver/federation/federation_grpc_federation.pb.go b/_examples/03_custom_resolver/federation/federation_grpc_federation.pb.go
index 065746b7..4c7dbde4 100644
--- a/_examples/03_custom_resolver/federation/federation_grpc_federation.pb.go
+++ b/_examples/03_custom_resolver/federation/federation_grpc_federation.pb.go
@@ -40,12 +40,15 @@ type FederationV2DevService_Federation_V2Dev_GetPostV2DevResponseArgument struct
 
 // Federation_V2Dev_PostV2DevArgument is argument for "federation.v2dev.PostV2dev" message.
 type FederationV2DevService_Federation_V2Dev_PostV2DevArgument struct {
-	Id     string
-	Post   *post.Post
-	Res    *post.GetPostResponse
-	Unused *Unused
-	User   *User
-	XDef4  *ForNameless
+	Id        string
+	NullCheck bool
+	Post      *post.Post
+	Res       *post.GetPostResponse
+	TypedNil  *TypedNil
+	Unused    *Unused
+	User      *User
+	XDef4     *ForNameless
+	XDef7     bool
 }
 
 // Federation_V2Dev_PostV2Dev_UserArgument is custom resolver's argument for "user" field of "federation.v2dev.PostV2dev" message.
@@ -57,6 +60,10 @@ type FederationV2DevService_Federation_V2Dev_PostV2Dev_UserArgument struct {
 type FederationV2DevService_Federation_V2Dev_RefArgument struct {
 }
 
+// Federation_V2Dev_TypedNilArgument is argument for "federation.v2dev.TypedNil" message.
+type FederationV2DevService_Federation_V2Dev_TypedNilArgument struct {
+}
+
 // Federation_V2Dev_UnusedArgument is argument for "federation.v2dev.Unused" message.
 type FederationV2DevService_Federation_V2Dev_UnusedArgument struct {
 	Foo string
@@ -121,6 +128,8 @@ type FederationV2DevServiceResolver interface {
 	Resolve_Federation_V2Dev_ForNameless(context.Context, *FederationV2DevService_Federation_V2Dev_ForNamelessArgument) (*ForNameless, error)
 	// Resolve_Federation_V2Dev_PostV2Dev_User implements resolver for "federation.v2dev.PostV2dev.user".
 	Resolve_Federation_V2Dev_PostV2Dev_User(context.Context, *FederationV2DevService_Federation_V2Dev_PostV2Dev_UserArgument) (*User, error)
+	// Resolve_Federation_V2Dev_TypedNil implements resolver for "federation.v2dev.TypedNil".
+	Resolve_Federation_V2Dev_TypedNil(context.Context, *FederationV2DevService_Federation_V2Dev_TypedNilArgument) (*TypedNil, error)
 	// Resolve_Federation_V2Dev_Unused implements resolver for "federation.v2dev.Unused".
 	Resolve_Federation_V2Dev_Unused(context.Context, *FederationV2DevService_Federation_V2Dev_UnusedArgument) (*Unused, error)
 	// Resolve_Federation_V2Dev_User implements resolver for "federation.v2dev.User".
@@ -179,6 +188,13 @@ func (FederationV2DevServiceUnimplementedResolver) Resolve_Federation_V2Dev_Post
 	return
 }
 
+// Resolve_Federation_V2Dev_TypedNil resolve "federation.v2dev.TypedNil".
+// This method always returns Unimplemented error.
+func (FederationV2DevServiceUnimplementedResolver) Resolve_Federation_V2Dev_TypedNil(context.Context, *FederationV2DevService_Federation_V2Dev_TypedNilArgument) (ret *TypedNil, e error) {
+	e = grpcfed.GRPCErrorf(grpcfed.UnimplementedCode, "method Resolve_Federation_V2Dev_TypedNil not implemented")
+	return
+}
+
 // Resolve_Federation_V2Dev_Unused resolve "federation.v2dev.Unused".
 // This method always returns Unimplemented error.
 func (FederationV2DevServiceUnimplementedResolver) Resolve_Federation_V2Dev_Unused(context.Context, *FederationV2DevService_Federation_V2Dev_UnusedArgument) (ret *Unused, e error) {
@@ -259,7 +275,8 @@ func NewFederationV2DevService(cfg FederationV2DevServiceConfig) (*FederationV2D
 		"grpc.federation.private.PostV2devArgument": {
 			"id": grpcfed.NewCELFieldType(grpcfed.CELStringType, "Id"),
 		},
-		"grpc.federation.private.RefArgument": {},
+		"grpc.federation.private.RefArgument":      {},
+		"grpc.federation.private.TypedNilArgument": {},
 		"grpc.federation.private.UnusedArgument": {
 			"foo": grpcfed.NewCELFieldType(grpcfed.CELStringType, "Foo"),
 		},
@@ -558,22 +575,29 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 	type localValueType struct {
 		*grpcfed.LocalValue
 		vars struct {
-			_def4  *ForNameless
-			post   *post.Post
-			res    *post.GetPostResponse
-			unused *Unused
-			user   *User
+			_def4      *ForNameless
+			_def7      bool
+			null_check bool
+			post       *post.Post
+			res        *post.GetPostResponse
+			typed_nil  *TypedNil
+			unused     *Unused
+			user       *User
 		}
 	}
 	value := &localValueType{LocalValue: grpcfed.NewLocalValue(ctx, s.celEnvOpts, "grpc.federation.private.PostV2devArgument", req)}
 	value.AddEnv(s.env)
 	// A tree view of message dependencies is shown below.
 	/*
-	               _def4 ─┐
-	              unused ─┤
-	   res ─┐             │
-	        post ─┐       │
-	                user ─┤
+	                        _def4 ─┐
+	        typed_nil ─┐           │
+	                        _def7 ─┤
+	        typed_nil ─┐           │
+	                   null_check ─┤
+	                       unused ─┤
+	   res ─┐                      │
+	             post ─┐           │
+	                         user ─┤
 	*/
 	eg, ctx1 := grpcfed.ErrorGroupWithContext(ctx)
 
@@ -623,6 +647,120 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 		return nil, nil
 	})
 
+	grpcfed.GoWithRecover(eg, func() (any, error) {
+
+		// This section's codes are generated by the following proto definition.
+		/*
+		   def {
+		     name: "typed_nil"
+		     message {
+		       name: "TypedNil"
+		     }
+		   }
+		*/
+		if err := grpcfed.EvalDef(ctx1, value, grpcfed.Def[*TypedNil, *localValueType]{
+			Name: `typed_nil`,
+			Type: grpcfed.CELObjectType("federation.v2dev.TypedNil"),
+			Setter: func(value *localValueType, v *TypedNil) error {
+				value.vars.typed_nil = v
+				return nil
+			},
+			Message: func(ctx context.Context, value *localValueType) (any, error) {
+				args := &FederationV2DevService_Federation_V2Dev_TypedNilArgument{}
+				ret, err := s.resolve_Federation_V2Dev_TypedNil(ctx, args)
+				if err != nil {
+					return nil, err
+				}
+				return ret, nil
+			},
+		}); err != nil {
+			grpcfed.RecordErrorToSpan(ctx1, err)
+			return nil, err
+		}
+
+		// This section's codes are generated by the following proto definition.
+		/*
+		   def {
+		     name: "_def7"
+		     if: "typed_nil == null"
+		     by: "grpc.federation.log.info('output typed_nil', {'result': typed_nil == null})"
+		   }
+		*/
+		if err := grpcfed.EvalDef(ctx1, value, grpcfed.Def[bool, *localValueType]{
+			If:           `typed_nil == null`,
+			IfCacheIndex: 9,
+			Name:         `_def7`,
+			Type:         grpcfed.CELBoolType,
+			Setter: func(value *localValueType, v bool) error {
+				value.vars._def7 = v
+				return nil
+			},
+			By:           `grpc.federation.log.info('output typed_nil', {'result': typed_nil == null})`,
+			ByCacheIndex: 10,
+		}); err != nil {
+			grpcfed.RecordErrorToSpan(ctx1, err)
+			return nil, err
+		}
+		return nil, nil
+	})
+
+	grpcfed.GoWithRecover(eg, func() (any, error) {
+
+		// This section's codes are generated by the following proto definition.
+		/*
+		   def {
+		     name: "typed_nil"
+		     message {
+		       name: "TypedNil"
+		     }
+		   }
+		*/
+		if err := grpcfed.EvalDef(ctx1, value, grpcfed.Def[*TypedNil, *localValueType]{
+			Name: `typed_nil`,
+			Type: grpcfed.CELObjectType("federation.v2dev.TypedNil"),
+			Setter: func(value *localValueType, v *TypedNil) error {
+				value.vars.typed_nil = v
+				return nil
+			},
+			Message: func(ctx context.Context, value *localValueType) (any, error) {
+				args := &FederationV2DevService_Federation_V2Dev_TypedNilArgument{}
+				ret, err := s.resolve_Federation_V2Dev_TypedNil(ctx, args)
+				if err != nil {
+					return nil, err
+				}
+				return ret, nil
+			},
+		}); err != nil {
+			grpcfed.RecordErrorToSpan(ctx1, err)
+			return nil, err
+		}
+
+		// This section's codes are generated by the following proto definition.
+		/*
+		   def {
+		     name: "null_check"
+		     if: "typed_nil == null"
+		     by: "true"
+		   }
+		*/
+		if err := grpcfed.EvalDef(ctx1, value, grpcfed.Def[bool, *localValueType]{
+			If:           `typed_nil == null`,
+			IfCacheIndex: 11,
+			Name:         `null_check`,
+			Type:         grpcfed.CELBoolType,
+			Setter: func(value *localValueType, v bool) error {
+				value.vars.null_check = v
+				return nil
+			},
+			By:           `true`,
+			ByCacheIndex: 12,
+		}); err != nil {
+			grpcfed.RecordErrorToSpan(ctx1, err)
+			return nil, err
+		}
+		return nil, nil
+	})
+
 	grpcfed.GoWithRecover(eg, func() (any, error) {
 
 		// This section's codes are generated by the following proto definition.
@@ -648,7 +786,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'foo'`,
-					CacheIndex: 9,
+					CacheIndex: 13,
 					Setter: func(v string) error {
 						args.Foo = v
 						return nil
@@ -694,7 +832,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `$.id`,
-					CacheIndex: 10,
+					CacheIndex: 14,
 					Setter: func(v string) error {
 						args.Id = v
 						return nil
@@ -732,7 +870,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 				return nil
 			},
 			By:           `res.post`,
-			ByCacheIndex: 11,
+			ByCacheIndex: 15,
 		}); err != nil {
 			grpcfed.RecordErrorToSpan(ctx1, err)
 			return nil, err
@@ -761,7 +899,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*post.Post]{
 					Value:      value,
 					Expr:       `post`,
-					CacheIndex: 12,
+					CacheIndex: 16,
 					Setter: func(v *post.Post) error {
 						args.Id = v.GetId()
 						args.Title = v.GetTitle()
@@ -790,11 +928,14 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 	}
 
 	// assign named parameters to message arguments to pass to the custom resolver.
+	req.NullCheck = value.vars.null_check
 	req.Post = value.vars.post
 	req.Res = value.vars.res
+	req.TypedNil = value.vars.typed_nil
 	req.Unused = value.vars.unused
 	req.User = value.vars.user
 	req.XDef4 = value.vars._def4
+	req.XDef7 = value.vars._def7
 
 	// create a message value to be returned.
 	ret := &PostV2Dev{}
@@ -815,6 +956,19 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_PostV2Dev(ctx context.
 			return nil, err
 		}
 	}
+	// (grpc.federation.field).by = "null_check"
+	if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[bool]{
+		Value:      value,
+		Expr:       `null_check`,
+		CacheIndex: 17,
+		Setter: func(v bool) error {
+			ret.NullCheck = v
+			return nil
+		},
+	}); err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		return nil, err
+	}
 
 	grpcfed.Logger(ctx).DebugContext(ctx, "resolved federation.v2dev.PostV2dev", slog.Any("federation.v2dev.PostV2dev", s.logvalue_Federation_V2Dev_PostV2Dev(ret)))
 	return ret, nil
@@ -843,7 +997,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_Ref(ctx context.Contex
 	if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 		Value:      value,
 		Expr:       `grpc.federation.env.a`,
-		CacheIndex: 13,
+		CacheIndex: 18,
 		Setter: func(v string) error {
 			ret.A = v
 			return nil
@@ -857,6 +1011,27 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_Ref(ctx context.Contex
 	return ret, nil
 }
 
+// resolve_Federation_V2Dev_TypedNil resolve "federation.v2dev.TypedNil" message.
+func (s *FederationV2DevService) resolve_Federation_V2Dev_TypedNil(ctx context.Context, req *FederationV2DevService_Federation_V2Dev_TypedNilArgument) (*TypedNil, error) {
+	ctx, span := s.tracer.Start(ctx, "federation.v2dev.TypedNil")
+	defer span.End()
+	ctx = grpcfed.WithLogger(ctx, grpcfed.Logger(ctx), grpcfed.LogAttrs(ctx)...)
+
+	grpcfed.Logger(ctx).DebugContext(ctx, "resolve federation.v2dev.TypedNil", slog.Any("message_args", s.logvalue_Federation_V2Dev_TypedNilArgument(req)))
+
+	// create a message value to be returned.
+	// `custom_resolver = true` in "grpc.federation.message" option.
+	ctx = grpcfed.WithLogger(ctx, grpcfed.Logger(ctx)) // create a new reference to logger.
+	ret, err := s.resolver.Resolve_Federation_V2Dev_TypedNil(ctx, req)
+	if err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		return nil, err
+	}
+
+	grpcfed.Logger(ctx).DebugContext(ctx, "resolved federation.v2dev.TypedNil", slog.Any("federation.v2dev.TypedNil", s.logvalue_Federation_V2Dev_TypedNil(ret)))
+	return ret, nil
+}
+
 // resolve_Federation_V2Dev_Unused resolve "federation.v2dev.Unused" message.
 func (s *FederationV2DevService) resolve_Federation_V2Dev_Unused(ctx context.Context, req *FederationV2DevService_Federation_V2Dev_UnusedArgument) (*Unused, error) {
 	ctx, span := s.tracer.Start(ctx, "federation.v2dev.Unused")
@@ -918,7 +1093,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_User(ctx context.Conte
 			if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 				Value:      value,
 				Expr:       `$.user_id`,
-				CacheIndex: 14,
+				CacheIndex: 19,
 				Setter: func(v string) error {
 					args.Id = v
 					return nil
@@ -955,7 +1130,7 @@ func (s *FederationV2DevService) resolve_Federation_V2Dev_User(ctx context.Conte
 			return nil
 		},
 		By:           `res.user`,
-		ByCacheIndex: 15,
+		ByCacheIndex: 20,
 	}); err != nil {
 		grpcfed.RecordErrorToSpan(ctx, err)
 		return nil, err
@@ -1063,6 +1238,7 @@ func (s *FederationV2DevService) logvalue_Federation_V2Dev_PostV2Dev(v *PostV2De
 		slog.String("title", v.GetTitle()),
 		slog.String("content", v.GetContent()),
 		slog.Any("user", s.logvalue_Federation_V2Dev_User(v.GetUser())),
+		slog.Bool("null_check", v.GetNullCheck()),
 	)
 }
 
@@ -1099,6 +1275,20 @@ func (s *FederationV2DevService) logvalue_Federation_V2Dev_RefArgument(v *Federa
 	return slog.GroupValue()
 }
 
+func (s *FederationV2DevService) logvalue_Federation_V2Dev_TypedNil(v *TypedNil) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue()
+}
+
+func (s *FederationV2DevService) logvalue_Federation_V2Dev_TypedNilArgument(v *FederationV2DevService_Federation_V2Dev_TypedNilArgument) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue()
+}
+
 func (s *FederationV2DevService) logvalue_Federation_V2Dev_Unused(v *Unused) slog.Value {
 	if v == nil {
 		return slog.GroupValue()
diff --git a/_examples/03_custom_resolver/main_test.go b/_examples/03_custom_resolver/main_test.go
index da1c25c0..1bcf4c8e 100644
--- a/_examples/03_custom_resolver/main_test.go
+++ b/_examples/03_custom_resolver/main_test.go
@@ -86,10 +86,14 @@ func (r *Resolver) Resolve_Federation_V2Dev_ForNameless(_ context.Context, _ *fe
 	return &federation.ForNameless{}, nil
 }
 
-func (r *Resolver) Resolve_Federation_V2Dev_User_Name(ctx context.Context, arg *federation.FederationV2DevService_Federation_V2Dev_User_NameArgument) (string, error) {
+func (r *Resolver) Resolve_Federation_V2Dev_User_Name(_ context.Context, arg *federation.FederationV2DevService_Federation_V2Dev_User_NameArgument) (string, error) {
 	return arg.Federation_V2Dev_User.Name, nil
 }
 
+func (r *Resolver) Resolve_Federation_V2Dev_TypedNil(_ context.Context, _ *federation.FederationV2DevService_Federation_V2Dev_TypedNilArgument) (*federation.TypedNil, error) {
+	return nil, nil
+}
+
 type PostServer struct {
 	*post.UnimplementedPostServiceServer
 }
@@ -246,6 +250,7 @@ func TestFederation(t *testing.T) {
 				Id:   "anonymous_id",
 				Name: "anonymous",
 			},
+			NullCheck: true,
 		},
 		EnvA:      "xxx",
 		EnvB:      2,
diff --git a/_examples/03_custom_resolver/proto/federation/federation.proto b/_examples/03_custom_resolver/proto/federation/federation.proto
index 8cd982e0..0b979185 100644
--- a/_examples/03_custom_resolver/proto/federation/federation.proto
+++ b/_examples/03_custom_resolver/proto/federation/federation.proto
@@ -101,18 +101,36 @@ message PostV2dev {
           args { name: "foo", by: "'foo'" }
         }
       },
-      { 
+      {
+        // without name
         message {
           name: "ForNameless"
           args { name: "bar", by: "'bar'" }
         }
-      } // without name
+      },
+      {
+        // assign typed-nil by custom resolver
+        name: "typed_nil"
+        message {
+          name: "TypedNil"
+        }
+      },
+      {
+        name: "null_check"
+        if: "typed_nil == null" // replace `grpc.federation.cast.null_value(typed_nil) == null` by EvalCEL function
+        by: "true"
+      },
+      {
+        if: "typed_nil == null"
+        by: "grpc.federation.log.info('output typed_nil', {'result': typed_nil == null})"
+      }
     ]
   };
   string id = 1;
   string title = 2;
   string content = 3;
   User user = 4 [(grpc.federation.field).custom_resolver = true];
+  bool null_check = 5 [(grpc.federation.field).by = "null_check"];
 }
 
 message User {
@@ -140,3 +158,7 @@ message ForNameless {
   option (grpc.federation.message).custom_resolver = true;
   string bar = 1;
 }
+
+message TypedNil {
+  option (grpc.federation.message).custom_resolver = true;
+}
\ No newline at end of file
diff --git a/_examples/10_oneof/federation/federation.pb.go b/_examples/10_oneof/federation/federation.pb.go
index b560dd87..db6e4f61 100644
--- a/_examples/10_oneof/federation/federation.pb.go
+++ b/_examples/10_oneof/federation/federation.pb.go
@@ -114,6 +114,91 @@ func (x *GetResponse) GetMsg() string {
 	return ""
 }
 
+type GetNoValueRequest struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+}
+
+func (x *GetNoValueRequest) Reset() {
+	*x = GetNoValueRequest{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_federation_federation_proto_msgTypes[2]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *GetNoValueRequest) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*GetNoValueRequest) ProtoMessage() {}
+
+func (x *GetNoValueRequest) ProtoReflect() protoreflect.Message {
+	mi := &file_federation_federation_proto_msgTypes[2]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use GetNoValueRequest.ProtoReflect.Descriptor instead.
+func (*GetNoValueRequest) Descriptor() ([]byte, []int) {
+	return file_federation_federation_proto_rawDescGZIP(), []int{2}
+}
+
+type GetNoValueResponse struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	NoValue *M `protobuf:"bytes,1,opt,name=no_value,json=noValue,proto3" json:"no_value,omitempty"`
+}
+
+func (x *GetNoValueResponse) Reset() {
+	*x = GetNoValueResponse{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_federation_federation_proto_msgTypes[3]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *GetNoValueResponse) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*GetNoValueResponse) ProtoMessage() {}
+
+func (x *GetNoValueResponse) ProtoReflect() protoreflect.Message {
+	mi := &file_federation_federation_proto_msgTypes[3]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use GetNoValueResponse.ProtoReflect.Descriptor instead.
+func (*GetNoValueResponse) Descriptor() ([]byte, []int) {
+	return file_federation_federation_proto_rawDescGZIP(), []int{3}
+}
+
+func (x *GetNoValueResponse) GetNoValue() *M {
+	if x != nil {
+		return x.NoValue
+	}
+	return nil
+}
+
 type UserSelection struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -130,7 +215,7 @@ type UserSelection struct {
 func (x *UserSelection) Reset() {
 	*x = UserSelection{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_federation_federation_proto_msgTypes[2]
+		mi := &file_federation_federation_proto_msgTypes[4]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -143,7 +228,7 @@ func (x *UserSelection) String() string {
 func (*UserSelection) ProtoMessage() {}
 
 func (x *UserSelection) ProtoReflect() protoreflect.Message {
-	mi := &file_federation_federation_proto_msgTypes[2]
+	mi := &file_federation_federation_proto_msgTypes[4]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -156,7 +241,7 @@ func (x *UserSelection) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use UserSelection.ProtoReflect.Descriptor instead.
 func (*UserSelection) Descriptor() ([]byte, []int) {
-	return file_federation_federation_proto_rawDescGZIP(), []int{2}
+	return file_federation_federation_proto_rawDescGZIP(), []int{4}
 }
 
 func (m *UserSelection) GetUser() isUserSelection_User {
@@ -225,7 +310,7 @@ type MessageSelection struct {
 func (x *MessageSelection) Reset() {
 	*x = MessageSelection{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_federation_federation_proto_msgTypes[3]
+		mi := &file_federation_federation_proto_msgTypes[5]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -238,7 +323,7 @@ func (x *MessageSelection) String() string {
 func (*MessageSelection) ProtoMessage() {}
 
 func (x *MessageSelection) ProtoReflect() protoreflect.Message {
-	mi := &file_federation_federation_proto_msgTypes[3]
+	mi := &file_federation_federation_proto_msgTypes[5]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -251,7 +336,7 @@ func (x *MessageSelection) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use MessageSelection.ProtoReflect.Descriptor instead.
 func (*MessageSelection) Descriptor() ([]byte, []int) {
-	return file_federation_federation_proto_rawDescGZIP(), []int{3}
+	return file_federation_federation_proto_rawDescGZIP(), []int{5}
 }
 
 func (m *MessageSelection) GetMessage() isMessageSelection_Message {
@@ -304,6 +389,87 @@ func (*MessageSelection_MsgB) isMessageSelection_Message() {}
 
 func (*MessageSelection_MsgC) isMessageSelection_Message() {}
 
+type NoValueSelection struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// Types that are assignable to NoValue:
+	//
+	//	*NoValueSelection_MA
+	//	*NoValueSelection_MB
+	NoValue isNoValueSelection_NoValue `protobuf_oneof:"no_value"`
+}
+
+func (x *NoValueSelection) Reset() {
+	*x = NoValueSelection{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_federation_federation_proto_msgTypes[6]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *NoValueSelection) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*NoValueSelection) ProtoMessage() {}
+
+func (x *NoValueSelection) ProtoReflect() protoreflect.Message {
+	mi := &file_federation_federation_proto_msgTypes[6]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use NoValueSelection.ProtoReflect.Descriptor instead.
+func (*NoValueSelection) Descriptor() ([]byte, []int) {
+	return file_federation_federation_proto_rawDescGZIP(), []int{6}
+}
+
+func (m *NoValueSelection) GetNoValue() isNoValueSelection_NoValue {
+	if m != nil {
+		return m.NoValue
+	}
+	return nil
+}
+
+func (x *NoValueSelection) GetMA() *M {
+	if x, ok := x.GetNoValue().(*NoValueSelection_MA); ok {
+		return x.MA
+	}
+	return nil
+}
+
+func (x *NoValueSelection) GetMB() *M {
+	if x, ok := x.GetNoValue().(*NoValueSelection_MB); ok {
+		return x.MB
+	}
+	return nil
+}
+
+type isNoValueSelection_NoValue interface {
+	isNoValueSelection_NoValue()
+}
+
+type NoValueSelection_MA struct {
+	MA *M `protobuf:"bytes,1,opt,name=m_a,json=mA,proto3,oneof"`
+}
+
+type NoValueSelection_MB struct {
+	MB *M `protobuf:"bytes,2,opt,name=m_b,json=mB,proto3,oneof"`
+}
+
+func (*NoValueSelection_MA) isNoValueSelection_NoValue() {}
+
+func (*NoValueSelection_MB) isNoValueSelection_NoValue() {}
+
 type M struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -315,7 +481,7 @@ type M struct {
 func (x *M) Reset() {
 	*x = M{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_federation_federation_proto_msgTypes[4]
+		mi := &file_federation_federation_proto_msgTypes[7]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -328,7 +494,7 @@ func (x *M) String() string {
 func (*M) ProtoMessage() {}
 
 func (x *M) ProtoReflect() protoreflect.Message {
-	mi := &file_federation_federation_proto_msgTypes[4]
+	mi := &file_federation_federation_proto_msgTypes[7]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -341,7 +507,7 @@ func (x *M) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use M.ProtoReflect.Descriptor instead.
 func (*M) Descriptor() ([]byte, []int) {
-	return file_federation_federation_proto_rawDescGZIP(), []int{4}
+	return file_federation_federation_proto_rawDescGZIP(), []int{7}
 }
 
 func (x *M) GetValue() string {
@@ -362,7 +528,7 @@ type User struct {
 func (x *User) Reset() {
 	*x = User{}
 	if protoimpl.UnsafeEnabled {
-		mi := &file_federation_federation_proto_msgTypes[5]
+		mi := &file_federation_federation_proto_msgTypes[8]
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		ms.StoreMessageInfo(mi)
 	}
@@ -375,7 +541,7 @@ func (x *User) String() string {
 func (*User) ProtoMessage() {}
 
 func (x *User) ProtoReflect() protoreflect.Message {
-	mi := &file_federation_federation_proto_msgTypes[5]
+	mi := &file_federation_federation_proto_msgTypes[8]
 	if protoimpl.UnsafeEnabled && x != nil {
 		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
 		if ms.LoadMessageInfo() == nil {
@@ -388,7 +554,7 @@ func (x *User) ProtoReflect() protoreflect.Message {
 
 // Deprecated: Use User.ProtoReflect.Descriptor instead.
 func (*User) Descriptor() ([]byte, []int) {
-	return file_federation_federation_proto_rawDescGZIP(), []int{5}
+	return file_federation_federation_proto_rawDescGZIP(), []int{8}
 }
 
 func (x *User) GetId() string {
@@ -418,70 +584,96 @@ var file_federation_federation_proto_rawDesc = []byte{
 	0x65, 0x72, 0x53, 0x65, 0x6c, 0x65, 0x63, 0x74, 0x69, 0x6f, 0x6e, 0x12, 0x0e, 0x0a, 0x05, 0x76,
 	0x61, 0x6c, 0x75, 0x65, 0x12, 0x05, 0x27, 0x66, 0x6f, 0x6f, 0x27, 0x0a, 0x1d, 0x0a, 0x07, 0x6d,
 	0x73, 0x67, 0x5f, 0x73, 0x65, 0x6c, 0x6a, 0x12, 0x0a, 0x10, 0x4d, 0x65, 0x73, 0x73, 0x61, 0x67,
-	0x65, 0x53, 0x65, 0x6c, 0x65, 0x63, 0x74, 0x69, 0x6f, 0x6e, 0x22, 0x80, 0x03, 0x0a, 0x0d, 0x55,
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+	0x65, 0x53, 0x65, 0x6c, 0x65, 0x63, 0x74, 0x69, 0x6f, 0x6e, 0x22, 0x13, 0x0a, 0x11, 0x47, 0x65,
+	0x74, 0x4e, 0x6f, 0x56, 0x61, 0x6c, 0x75, 0x65, 0x52, 0x65, 0x71, 0x75, 0x65, 0x73, 0x74, 0x22,
+	0x87, 0x01, 0x0a, 0x12, 0x47, 0x65, 0x74, 0x4e, 0x6f, 0x56, 0x61, 0x6c, 0x75, 0x65, 0x52, 0x65,
+	0x73, 0x70, 0x6f, 0x6e, 0x73, 0x65, 0x12, 0x48, 0x0a, 0x08, 0x6e, 0x6f, 0x5f, 0x76, 0x61, 0x6c,
+	0x75, 0x65, 0x18, 0x01, 0x20, 0x01, 0x28, 0x0b, 0x32, 0x11, 0x2e, 0x6f, 0x72, 0x67, 0x2e, 0x66,
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+	0x12, 0x15, 0x6e, 0x6f, 0x5f, 0x76, 0x61, 0x6c, 0x75, 0x65, 0x5f, 0x73, 0x65, 0x6c, 0x2e, 0x6e,
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+	0x58, 0xaa, 0x02, 0x0e, 0x4f, 0x72, 0x67, 0x2e, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69,
+	0x6f, 0x6e, 0xca, 0x02, 0x0e, 0x4f, 0x72, 0x67, 0x5c, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74,
+	0x69, 0x6f, 0x6e, 0xe2, 0x02, 0x1a, 0x4f, 0x72, 0x67, 0x5c, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61,
+	0x74, 0x69, 0x6f, 0x6e, 0x5c, 0x47, 0x50, 0x42, 0x4d, 0x65, 0x74, 0x61, 0x64, 0x61, 0x74, 0x61,
+	0xea, 0x02, 0x0f, 0x4f, 0x72, 0x67, 0x3a, 0x3a, 0x46, 0x65, 0x64, 0x65, 0x72, 0x61, 0x74, 0x69,
+	0x6f, 0x6e, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -496,27 +688,35 @@ func file_federation_federation_proto_rawDescGZIP() []byte {
 	return file_federation_federation_proto_rawDescData
 }
 
-var file_federation_federation_proto_msgTypes = make([]protoimpl.MessageInfo, 6)
+var file_federation_federation_proto_msgTypes = make([]protoimpl.MessageInfo, 9)
 var file_federation_federation_proto_goTypes = []interface{}{
-	(*GetRequest)(nil),       // 0: org.federation.GetRequest
-	(*GetResponse)(nil),      // 1: org.federation.GetResponse
-	(*UserSelection)(nil),    // 2: org.federation.UserSelection
-	(*MessageSelection)(nil), // 3: org.federation.MessageSelection
-	(*M)(nil),                // 4: org.federation.M
-	(*User)(nil),             // 5: org.federation.User
+	(*GetRequest)(nil),         // 0: org.federation.GetRequest
+	(*GetResponse)(nil),        // 1: org.federation.GetResponse
+	(*GetNoValueRequest)(nil),  // 2: org.federation.GetNoValueRequest
+	(*GetNoValueResponse)(nil), // 3: org.federation.GetNoValueResponse
+	(*UserSelection)(nil),      // 4: org.federation.UserSelection
+	(*MessageSelection)(nil),   // 5: org.federation.MessageSelection
+	(*NoValueSelection)(nil),   // 6: org.federation.NoValueSelection
+	(*M)(nil),                  // 7: org.federation.M
+	(*User)(nil),               // 8: org.federation.User
 }
 var file_federation_federation_proto_depIdxs = []int32{
-	5, // 0: org.federation.GetResponse.user:type_name -> org.federation.User
-	5, // 1: org.federation.UserSelection.user_a:type_name -> org.federation.User
-	5, // 2: org.federation.UserSelection.user_b:type_name -> org.federation.User
-	5, // 3: org.federation.UserSelection.user_c:type_name -> org.federation.User
-	0, // 4: org.federation.FederationService.Get:input_type -> org.federation.GetRequest
-	1, // 5: org.federation.FederationService.Get:output_type -> org.federation.GetResponse
-	5, // [5:6] is the sub-list for method output_type
-	4, // [4:5] is the sub-list for method input_type
-	4, // [4:4] is the sub-list for extension type_name
-	4, // [4:4] is the sub-list for extension extendee
-	0, // [0:4] is the sub-list for field type_name
+	8, // 0: org.federation.GetResponse.user:type_name -> org.federation.User
+	7, // 1: org.federation.GetNoValueResponse.no_value:type_name -> org.federation.M
+	8, // 2: org.federation.UserSelection.user_a:type_name -> org.federation.User
+	8, // 3: org.federation.UserSelection.user_b:type_name -> org.federation.User
+	8, // 4: org.federation.UserSelection.user_c:type_name -> org.federation.User
+	7, // 5: org.federation.NoValueSelection.m_a:type_name -> org.federation.M
+	7, // 6: org.federation.NoValueSelection.m_b:type_name -> org.federation.M
+	0, // 7: org.federation.FederationService.Get:input_type -> org.federation.GetRequest
+	2, // 8: org.federation.FederationService.GetNoValue:input_type -> org.federation.GetNoValueRequest
+	1, // 9: org.federation.FederationService.Get:output_type -> org.federation.GetResponse
+	3, // 10: org.federation.FederationService.GetNoValue:output_type -> org.federation.GetNoValueResponse
+	9, // [9:11] is the sub-list for method output_type
+	7, // [7:9] is the sub-list for method input_type
+	7, // [7:7] is the sub-list for extension type_name
+	7, // [7:7] is the sub-list for extension extendee
+	0, // [0:7] is the sub-list for field type_name
 }
 
 func init() { file_federation_federation_proto_init() }
@@ -550,7 +750,7 @@ func file_federation_federation_proto_init() {
 			}
 		}
 		file_federation_federation_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*UserSelection); i {
+			switch v := v.(*GetNoValueRequest); i {
 			case 0:
 				return &v.state
 			case 1:
@@ -562,7 +762,7 @@ func file_federation_federation_proto_init() {
 			}
 		}
 		file_federation_federation_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*MessageSelection); i {
+			switch v := v.(*GetNoValueResponse); i {
 			case 0:
 				return &v.state
 			case 1:
@@ -574,7 +774,7 @@ func file_federation_federation_proto_init() {
 			}
 		}
 		file_federation_federation_proto_msgTypes[4].Exporter = func(v interface{}, i int) interface{} {
-			switch v := v.(*M); i {
+			switch v := v.(*UserSelection); i {
 			case 0:
 				return &v.state
 			case 1:
@@ -586,6 +786,42 @@ func file_federation_federation_proto_init() {
 			}
 		}
 		file_federation_federation_proto_msgTypes[5].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*MessageSelection); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_federation_federation_proto_msgTypes[6].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*NoValueSelection); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_federation_federation_proto_msgTypes[7].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*M); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_federation_federation_proto_msgTypes[8].Exporter = func(v interface{}, i int) interface{} {
 			switch v := v.(*User); i {
 			case 0:
 				return &v.state
@@ -598,23 +834,27 @@ func file_federation_federation_proto_init() {
 			}
 		}
 	}
-	file_federation_federation_proto_msgTypes[2].OneofWrappers = []interface{}{
+	file_federation_federation_proto_msgTypes[4].OneofWrappers = []interface{}{
 		(*UserSelection_UserA)(nil),
 		(*UserSelection_UserB)(nil),
 		(*UserSelection_UserC)(nil),
 	}
-	file_federation_federation_proto_msgTypes[3].OneofWrappers = []interface{}{
+	file_federation_federation_proto_msgTypes[5].OneofWrappers = []interface{}{
 		(*MessageSelection_MsgA)(nil),
 		(*MessageSelection_MsgB)(nil),
 		(*MessageSelection_MsgC)(nil),
 	}
+	file_federation_federation_proto_msgTypes[6].OneofWrappers = []interface{}{
+		(*NoValueSelection_MA)(nil),
+		(*NoValueSelection_MB)(nil),
+	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
 		File: protoimpl.DescBuilder{
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_federation_federation_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   6,
+			NumMessages:   9,
 			NumExtensions: 0,
 			NumServices:   1,
 		},
diff --git a/_examples/10_oneof/federation/federation_grpc.pb.go b/_examples/10_oneof/federation/federation_grpc.pb.go
index 01b0a9e9..e24f84d5 100644
--- a/_examples/10_oneof/federation/federation_grpc.pb.go
+++ b/_examples/10_oneof/federation/federation_grpc.pb.go
@@ -19,7 +19,8 @@ import (
 const _ = grpc.SupportPackageIsVersion7
 
 const (
-	FederationService_Get_FullMethodName = "/org.federation.FederationService/Get"
+	FederationService_Get_FullMethodName        = "/org.federation.FederationService/Get"
+	FederationService_GetNoValue_FullMethodName = "/org.federation.FederationService/GetNoValue"
 )
 
 // FederationServiceClient is the client API for FederationService service.
@@ -27,6 +28,7 @@ const (
 // For semantics around ctx use and closing/ending streaming RPCs, please refer to https://pkg.go.dev/google.golang.org/grpc/?tab=doc#ClientConn.NewStream.
 type FederationServiceClient interface {
 	Get(ctx context.Context, in *GetRequest, opts ...grpc.CallOption) (*GetResponse, error)
+	GetNoValue(ctx context.Context, in *GetNoValueRequest, opts ...grpc.CallOption) (*GetNoValueResponse, error)
 }
 
 type federationServiceClient struct {
@@ -46,11 +48,21 @@ func (c *federationServiceClient) Get(ctx context.Context, in *GetRequest, opts
 	return out, nil
 }
 
+func (c *federationServiceClient) GetNoValue(ctx context.Context, in *GetNoValueRequest, opts ...grpc.CallOption) (*GetNoValueResponse, error) {
+	out := new(GetNoValueResponse)
+	err := c.cc.Invoke(ctx, FederationService_GetNoValue_FullMethodName, in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // FederationServiceServer is the server API for FederationService service.
 // All implementations must embed UnimplementedFederationServiceServer
 // for forward compatibility
 type FederationServiceServer interface {
 	Get(context.Context, *GetRequest) (*GetResponse, error)
+	GetNoValue(context.Context, *GetNoValueRequest) (*GetNoValueResponse, error)
 	mustEmbedUnimplementedFederationServiceServer()
 }
 
@@ -61,6 +73,9 @@ type UnimplementedFederationServiceServer struct {
 func (UnimplementedFederationServiceServer) Get(context.Context, *GetRequest) (*GetResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method Get not implemented")
 }
+func (UnimplementedFederationServiceServer) GetNoValue(context.Context, *GetNoValueRequest) (*GetNoValueResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method GetNoValue not implemented")
+}
 func (UnimplementedFederationServiceServer) mustEmbedUnimplementedFederationServiceServer() {}
 
 // UnsafeFederationServiceServer may be embedded to opt out of forward compatibility for this service.
@@ -92,6 +107,24 @@ func _FederationService_Get_Handler(srv interface{}, ctx context.Context, dec fu
 	return interceptor(ctx, in, info, handler)
 }
 
+func _FederationService_GetNoValue_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetNoValueRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(FederationServiceServer).GetNoValue(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: FederationService_GetNoValue_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(FederationServiceServer).GetNoValue(ctx, req.(*GetNoValueRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 // FederationService_ServiceDesc is the grpc.ServiceDesc for FederationService service.
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
@@ -103,6 +136,10 @@ var FederationService_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "Get",
 			Handler:    _FederationService_Get_Handler,
 		},
+		{
+			MethodName: "GetNoValue",
+			Handler:    _FederationService_GetNoValue_Handler,
+		},
 	},
 	Streams:  []grpc.StreamDesc{},
 	Metadata: "federation/federation.proto",
diff --git a/_examples/10_oneof/federation/federation_grpc_federation.pb.go b/_examples/10_oneof/federation/federation_grpc_federation.pb.go
index de9f3206..4b48e0b2 100644
--- a/_examples/10_oneof/federation/federation_grpc_federation.pb.go
+++ b/_examples/10_oneof/federation/federation_grpc_federation.pb.go
@@ -24,6 +24,11 @@ var (
 	_ = reflect.Invalid // to avoid "imported and not used error"
 )
 
+// Org_Federation_GetNoValueResponseArgument is argument for "org.federation.GetNoValueResponse" message.
+type FederationService_Org_Federation_GetNoValueResponseArgument struct {
+	NoValueSel *NoValueSelection
+}
+
 // Org_Federation_GetResponseArgument is argument for "org.federation.GetResponse" message.
 type FederationService_Org_Federation_GetResponseArgument struct {
 	MsgSel *MessageSelection
@@ -34,6 +39,10 @@ type FederationService_Org_Federation_GetResponseArgument struct {
 type FederationService_Org_Federation_MessageSelectionArgument struct {
 }
 
+// Org_Federation_NoValueSelectionArgument is argument for "org.federation.NoValueSelection" message.
+type FederationService_Org_Federation_NoValueSelectionArgument struct {
+}
+
 // Org_Federation_UserArgument is argument for "org.federation.User" message.
 type FederationService_Org_Federation_UserArgument struct {
 	Bar    string
@@ -135,8 +144,10 @@ func NewFederationService(cfg FederationServiceConfig) (*FederationService, erro
 		errorHandler = func(ctx context.Context, methodName string, err error) error { return err }
 	}
 	celTypeHelperFieldMap := grpcfed.CELTypeHelperFieldMap{
-		"grpc.federation.private.GetResponseArgument":      {},
-		"grpc.federation.private.MessageSelectionArgument": {},
+		"grpc.federation.private.GetNoValueResponseArgument": {},
+		"grpc.federation.private.GetResponseArgument":        {},
+		"grpc.federation.private.MessageSelectionArgument":   {},
+		"grpc.federation.private.NoValueSelectionArgument":   {},
 		"grpc.federation.private.UserArgument": {
 			"user_id": grpcfed.NewCELFieldType(grpcfed.CELStringType, "UserId"),
 			"foo":     grpcfed.NewCELFieldType(grpcfed.CELIntType, "Foo"),
@@ -153,6 +164,14 @@ func NewFederationService(cfg FederationServiceConfig) (*FederationService, erro
 				reflect.Zero(reflect.TypeOf("")),
 			),
 		},
+		"org.federation.NoValueSelection": {
+			"no_value": grpcfed.NewOneofSelectorFieldType(
+				grpcfed.NewCELObjectType("org.federation.M"), "NoValue",
+				[]reflect.Type{reflect.TypeOf((*NoValueSelection_MA)(nil)), reflect.TypeOf((*NoValueSelection_MB)(nil))},
+				[]string{"GetMA", "GetMB"},
+				reflect.Zero(reflect.TypeOf((*M)(nil))),
+			),
+		},
 		"org.federation.UserSelection": {
 			"user": grpcfed.NewOneofSelectorFieldType(
 				grpcfed.NewCELObjectType("org.federation.User"), "User",
@@ -200,6 +219,96 @@ func (s *FederationService) Get(ctx context.Context, req *GetRequest) (res *GetR
 	return res, nil
 }
 
+// GetNoValue implements "org.federation.FederationService/GetNoValue" method.
+func (s *FederationService) GetNoValue(ctx context.Context, req *GetNoValueRequest) (res *GetNoValueResponse, e error) {
+	ctx, span := s.tracer.Start(ctx, "org.federation.FederationService/GetNoValue")
+	defer span.End()
+	ctx = grpcfed.WithLogger(ctx, s.logger)
+	ctx = grpcfed.WithCELCacheMap(ctx, s.celCacheMap)
+	defer func() {
+		if r := recover(); r != nil {
+			e = grpcfed.RecoverError(r, grpcfed.StackTrace())
+			grpcfed.OutputErrorLog(ctx, e)
+		}
+	}()
+	res, err := s.resolve_Org_Federation_GetNoValueResponse(ctx, &FederationService_Org_Federation_GetNoValueResponseArgument{})
+	if err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		grpcfed.OutputErrorLog(ctx, err)
+		return nil, err
+	}
+	return res, nil
+}
+
+// resolve_Org_Federation_GetNoValueResponse resolve "org.federation.GetNoValueResponse" message.
+func (s *FederationService) resolve_Org_Federation_GetNoValueResponse(ctx context.Context, req *FederationService_Org_Federation_GetNoValueResponseArgument) (*GetNoValueResponse, error) {
+	ctx, span := s.tracer.Start(ctx, "org.federation.GetNoValueResponse")
+	defer span.End()
+	ctx = grpcfed.WithLogger(ctx, grpcfed.Logger(ctx), grpcfed.LogAttrs(ctx)...)
+
+	grpcfed.Logger(ctx).DebugContext(ctx, "resolve org.federation.GetNoValueResponse", slog.Any("message_args", s.logvalue_Org_Federation_GetNoValueResponseArgument(req)))
+	type localValueType struct {
+		*grpcfed.LocalValue
+		vars struct {
+			no_value_sel *NoValueSelection
+		}
+	}
+	value := &localValueType{LocalValue: grpcfed.NewLocalValue(ctx, s.celEnvOpts, "grpc.federation.private.GetNoValueResponseArgument", req)}
+
+	// This section's codes are generated by the following proto definition.
+	/*
+	   def {
+	     name: "no_value_sel"
+	     message {
+	       name: "NoValueSelection"
+	     }
+	   }
+	*/
+	if err := grpcfed.EvalDef(ctx, value, grpcfed.Def[*NoValueSelection, *localValueType]{
+		Name: `no_value_sel`,
+		Type: grpcfed.CELObjectType("org.federation.NoValueSelection"),
+		Setter: func(value *localValueType, v *NoValueSelection) error {
+			value.vars.no_value_sel = v
+			return nil
+		},
+		Message: func(ctx context.Context, value *localValueType) (any, error) {
+			args := &FederationService_Org_Federation_NoValueSelectionArgument{}
+			ret, err := s.resolve_Org_Federation_NoValueSelection(ctx, args)
+			if err != nil {
+				return nil, err
+			}
+			return ret, nil
+		},
+	}); err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		return nil, err
+	}
+
+	// assign named parameters to message arguments to pass to the custom resolver.
+	req.NoValueSel = value.vars.no_value_sel
+
+	// create a message value to be returned.
+	ret := &GetNoValueResponse{}
+
+	// field binding section.
+	// (grpc.federation.field).by = "no_value_sel.no_value"
+	if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*M]{
+		Value:      value,
+		Expr:       `no_value_sel.no_value`,
+		CacheIndex: 1,
+		Setter: func(v *M) error {
+			ret.NoValue = v
+			return nil
+		},
+	}); err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		return nil, err
+	}
+
+	grpcfed.Logger(ctx).DebugContext(ctx, "resolved org.federation.GetNoValueResponse", slog.Any("org.federation.GetNoValueResponse", s.logvalue_Org_Federation_GetNoValueResponse(ret)))
+	return ret, nil
+}
+
 // resolve_Org_Federation_GetResponse resolve "org.federation.GetResponse" message.
 func (s *FederationService) resolve_Org_Federation_GetResponse(ctx context.Context, req *FederationService_Org_Federation_GetResponseArgument) (*GetResponse, error) {
 	ctx, span := s.tracer.Start(ctx, "org.federation.GetResponse")
@@ -280,7 +389,7 @@ func (s *FederationService) resolve_Org_Federation_GetResponse(ctx context.Conte
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'foo'`,
-					CacheIndex: 1,
+					CacheIndex: 2,
 					Setter: func(v string) error {
 						args.Value = v
 						return nil
@@ -317,7 +426,7 @@ func (s *FederationService) resolve_Org_Federation_GetResponse(ctx context.Conte
 	if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*User]{
 		Value:      value,
 		Expr:       `sel.user`,
-		CacheIndex: 2,
+		CacheIndex: 3,
 		Setter: func(v *User) error {
 			ret.User = v
 			return nil
@@ -330,7 +439,7 @@ func (s *FederationService) resolve_Org_Federation_GetResponse(ctx context.Conte
 	if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 		Value:      value,
 		Expr:       `msg_sel.message`,
-		CacheIndex: 3,
+		CacheIndex: 4,
 		Setter: func(v string) error {
 			ret.Msg = v
 			return nil
@@ -366,7 +475,7 @@ func (s *FederationService) resolve_Org_Federation_MessageSelection(ctx context.
 		Value:      value,
 		Expr:       `false`,
 		OutType:    reflect.TypeOf(true),
-		CacheIndex: 4,
+		CacheIndex: 5,
 	})
 	if err != nil {
 		grpcfed.RecordErrorToSpan(ctx, err)
@@ -376,7 +485,7 @@ func (s *FederationService) resolve_Org_Federation_MessageSelection(ctx context.
 		Value:      value,
 		Expr:       `true`,
 		OutType:    reflect.TypeOf(true),
-		CacheIndex: 5,
+		CacheIndex: 6,
 	})
 	if err != nil {
 		grpcfed.RecordErrorToSpan(ctx, err)
@@ -388,7 +497,7 @@ func (s *FederationService) resolve_Org_Federation_MessageSelection(ctx context.
 		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 			Value:      value,
 			Expr:       `'aaa'`,
-			CacheIndex: 6,
+			CacheIndex: 7,
 			Setter: func(v string) error {
 				ret.Message = &MessageSelection_MsgA{MsgA: v}
 				return nil
@@ -402,7 +511,7 @@ func (s *FederationService) resolve_Org_Federation_MessageSelection(ctx context.
 		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 			Value:      value,
 			Expr:       `'bbb'`,
-			CacheIndex: 7,
+			CacheIndex: 8,
 			Setter: func(v string) error {
 				ret.Message = &MessageSelection_MsgB{MsgB: v}
 				return nil
@@ -416,7 +525,7 @@ func (s *FederationService) resolve_Org_Federation_MessageSelection(ctx context.
 		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 			Value:      value,
 			Expr:       `'ccc'`,
-			CacheIndex: 8,
+			CacheIndex: 9,
 			Setter: func(v string) error {
 				ret.Message = &MessageSelection_MsgC{MsgC: v}
 				return nil
@@ -431,6 +540,79 @@ func (s *FederationService) resolve_Org_Federation_MessageSelection(ctx context.
 	return ret, nil
 }
 
+// resolve_Org_Federation_NoValueSelection resolve "org.federation.NoValueSelection" message.
+func (s *FederationService) resolve_Org_Federation_NoValueSelection(ctx context.Context, req *FederationService_Org_Federation_NoValueSelectionArgument) (*NoValueSelection, error) {
+	ctx, span := s.tracer.Start(ctx, "org.federation.NoValueSelection")
+	defer span.End()
+	ctx = grpcfed.WithLogger(ctx, grpcfed.Logger(ctx), grpcfed.LogAttrs(ctx)...)
+
+	grpcfed.Logger(ctx).DebugContext(ctx, "resolve org.federation.NoValueSelection", slog.Any("message_args", s.logvalue_Org_Federation_NoValueSelectionArgument(req)))
+	type localValueType struct {
+		*grpcfed.LocalValue
+		vars struct {
+		}
+	}
+	value := &localValueType{LocalValue: grpcfed.NewLocalValue(ctx, s.celEnvOpts, "grpc.federation.private.NoValueSelectionArgument", req)}
+
+	// create a message value to be returned.
+	ret := &NoValueSelection{}
+
+	// field binding section.
+	oneof_MA, err := grpcfed.EvalCEL(ctx, &grpcfed.EvalCELRequest{
+		Value:      value,
+		Expr:       `false`,
+		OutType:    reflect.TypeOf(true),
+		CacheIndex: 10,
+	})
+	if err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		return nil, err
+	}
+	oneof_MB, err := grpcfed.EvalCEL(ctx, &grpcfed.EvalCELRequest{
+		Value:      value,
+		Expr:       `false`,
+		OutType:    reflect.TypeOf(true),
+		CacheIndex: 11,
+	})
+	if err != nil {
+		grpcfed.RecordErrorToSpan(ctx, err)
+		return nil, err
+	}
+	switch {
+	case oneof_MA.(bool):
+
+		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*M]{
+			Value:      value,
+			Expr:       `M{value: 'a'}`,
+			CacheIndex: 12,
+			Setter: func(v *M) error {
+				ret.NoValue = &NoValueSelection_MA{MA: v}
+				return nil
+			},
+		}); err != nil {
+			grpcfed.RecordErrorToSpan(ctx, err)
+			return nil, err
+		}
+	case oneof_MB.(bool):
+
+		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*M]{
+			Value:      value,
+			Expr:       `M{value: 'b'}`,
+			CacheIndex: 13,
+			Setter: func(v *M) error {
+				ret.NoValue = &NoValueSelection_MB{MB: v}
+				return nil
+			},
+		}); err != nil {
+			grpcfed.RecordErrorToSpan(ctx, err)
+			return nil, err
+		}
+	}
+
+	grpcfed.Logger(ctx).DebugContext(ctx, "resolved org.federation.NoValueSelection", slog.Any("org.federation.NoValueSelection", s.logvalue_Org_Federation_NoValueSelection(ret)))
+	return ret, nil
+}
+
 // resolve_Org_Federation_User resolve "org.federation.User" message.
 func (s *FederationService) resolve_Org_Federation_User(ctx context.Context, req *FederationService_Org_Federation_UserArgument) (*User, error) {
 	ctx, span := s.tracer.Start(ctx, "org.federation.User")
@@ -473,7 +655,7 @@ func (s *FederationService) resolve_Org_Federation_User(ctx context.Context, req
 			if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 				Value:      value,
 				Expr:       `$.user_id`,
-				CacheIndex: 9,
+				CacheIndex: 14,
 				Setter: func(v string) error {
 					args.Id = v
 					return nil
@@ -485,12 +667,12 @@ func (s *FederationService) resolve_Org_Federation_User(ctx context.Context, req
 			if err := grpcfed.If(ctx, &grpcfed.IfParam[*localValueType]{
 				Value:      value,
 				Expr:       `$.foo != 0`,
-				CacheIndex: 10,
+				CacheIndex: 15,
 				Body: func(value *localValueType) error {
 					return grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[int64]{
 						Value:      value,
 						Expr:       `$.foo`,
-						CacheIndex: 11,
+						CacheIndex: 16,
 						Setter: func(v int64) error {
 							args.Foobar = &user.GetUserRequest_Foo{
 								Foo: v,
@@ -506,12 +688,12 @@ func (s *FederationService) resolve_Org_Federation_User(ctx context.Context, req
 			if err := grpcfed.If(ctx, &grpcfed.IfParam[*localValueType]{
 				Value:      value,
 				Expr:       `$.bar != ''`,
-				CacheIndex: 12,
+				CacheIndex: 17,
 				Body: func(value *localValueType) error {
 					return grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 						Value:      value,
 						Expr:       `$.bar`,
-						CacheIndex: 13,
+						CacheIndex: 18,
 						Setter: func(v string) error {
 							args.Foobar = &user.GetUserRequest_Bar{
 								Bar: v,
@@ -545,7 +727,7 @@ func (s *FederationService) resolve_Org_Federation_User(ctx context.Context, req
 	if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 		Value:      value,
 		Expr:       `$.user_id`,
-		CacheIndex: 14,
+		CacheIndex: 19,
 		Setter: func(v string) error {
 			ret.Id = v
 			return nil
@@ -589,7 +771,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 		Value:      value,
 		Expr:       `false`,
 		OutType:    reflect.TypeOf(true),
-		CacheIndex: 15,
+		CacheIndex: 20,
 	})
 	if err != nil {
 		grpcfed.RecordErrorToSpan(ctx, err)
@@ -599,7 +781,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 		Value:      value,
 		Expr:       `true`,
 		OutType:    reflect.TypeOf(true),
-		CacheIndex: 16,
+		CacheIndex: 21,
 	})
 	if err != nil {
 		grpcfed.RecordErrorToSpan(ctx, err)
@@ -635,7 +817,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'a'`,
-					CacheIndex: 17,
+					CacheIndex: 22,
 					Setter: func(v string) error {
 						args.UserId = v
 						return nil
@@ -647,7 +829,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[int64]{
 					Value:      value,
 					Expr:       `0`,
-					CacheIndex: 18,
+					CacheIndex: 23,
 					Setter: func(v int64) error {
 						args.Foo = v
 						return nil
@@ -659,7 +841,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'hello'`,
-					CacheIndex: 19,
+					CacheIndex: 24,
 					Setter: func(v string) error {
 						args.Bar = v
 						return nil
@@ -680,7 +862,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*User]{
 			Value:      value,
 			Expr:       `ua`,
-			CacheIndex: 20,
+			CacheIndex: 25,
 			Setter: func(v *User) error {
 				ret.User = &UserSelection_UserA{UserA: v}
 				return nil
@@ -718,7 +900,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'b'`,
-					CacheIndex: 21,
+					CacheIndex: 26,
 					Setter: func(v string) error {
 						args.UserId = v
 						return nil
@@ -730,7 +912,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[int64]{
 					Value:      value,
 					Expr:       `0`,
-					CacheIndex: 22,
+					CacheIndex: 27,
 					Setter: func(v int64) error {
 						args.Foo = v
 						return nil
@@ -742,7 +924,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'hello'`,
-					CacheIndex: 23,
+					CacheIndex: 28,
 					Setter: func(v string) error {
 						args.Bar = v
 						return nil
@@ -763,7 +945,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*User]{
 			Value:      value,
 			Expr:       `ub`,
-			CacheIndex: 24,
+			CacheIndex: 29,
 			Setter: func(v *User) error {
 				ret.User = &UserSelection_UserB{UserB: v}
 				return nil
@@ -801,7 +983,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `$.value`,
-					CacheIndex: 25,
+					CacheIndex: 30,
 					Setter: func(v string) error {
 						args.UserId = v
 						return nil
@@ -813,7 +995,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[int64]{
 					Value:      value,
 					Expr:       `0`,
-					CacheIndex: 26,
+					CacheIndex: 31,
 					Setter: func(v int64) error {
 						args.Foo = v
 						return nil
@@ -825,7 +1007,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 				if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[string]{
 					Value:      value,
 					Expr:       `'hello'`,
-					CacheIndex: 27,
+					CacheIndex: 32,
 					Setter: func(v string) error {
 						args.Bar = v
 						return nil
@@ -846,7 +1028,7 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 		if err := grpcfed.SetCELValue(ctx, &grpcfed.SetCELValueParam[*User]{
 			Value:      value,
 			Expr:       `uc`,
-			CacheIndex: 28,
+			CacheIndex: 33,
 			Setter: func(v *User) error {
 				ret.User = &UserSelection_UserC{UserC: v}
 				return nil
@@ -861,6 +1043,22 @@ func (s *FederationService) resolve_Org_Federation_UserSelection(ctx context.Con
 	return ret, nil
 }
 
+func (s *FederationService) logvalue_Org_Federation_GetNoValueResponse(v *GetNoValueResponse) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue(
+		slog.Any("no_value", s.logvalue_Org_Federation_M(v.GetNoValue())),
+	)
+}
+
+func (s *FederationService) logvalue_Org_Federation_GetNoValueResponseArgument(v *FederationService_Org_Federation_GetNoValueResponseArgument) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue()
+}
+
 func (s *FederationService) logvalue_Org_Federation_GetResponse(v *GetResponse) slog.Value {
 	if v == nil {
 		return slog.GroupValue()
@@ -878,6 +1076,15 @@ func (s *FederationService) logvalue_Org_Federation_GetResponseArgument(v *Feder
 	return slog.GroupValue()
 }
 
+func (s *FederationService) logvalue_Org_Federation_M(v *M) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue(
+		slog.String("value", v.GetValue()),
+	)
+}
+
 func (s *FederationService) logvalue_Org_Federation_MessageSelection(v *MessageSelection) slog.Value {
 	if v == nil {
 		return slog.GroupValue()
@@ -896,6 +1103,23 @@ func (s *FederationService) logvalue_Org_Federation_MessageSelectionArgument(v *
 	return slog.GroupValue()
 }
 
+func (s *FederationService) logvalue_Org_Federation_NoValueSelection(v *NoValueSelection) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue(
+		slog.Any("m_a", s.logvalue_Org_Federation_M(v.GetMA())),
+		slog.Any("m_b", s.logvalue_Org_Federation_M(v.GetMB())),
+	)
+}
+
+func (s *FederationService) logvalue_Org_Federation_NoValueSelectionArgument(v *FederationService_Org_Federation_NoValueSelectionArgument) slog.Value {
+	if v == nil {
+		return slog.GroupValue()
+	}
+	return slog.GroupValue()
+}
+
 func (s *FederationService) logvalue_Org_Federation_User(v *User) slog.Value {
 	if v == nil {
 		return slog.GroupValue()
diff --git a/_examples/10_oneof/main_test.go b/_examples/10_oneof/main_test.go
index 8b1a6d04..ddf93699 100644
--- a/_examples/10_oneof/main_test.go
+++ b/_examples/10_oneof/main_test.go
@@ -17,6 +17,8 @@ import (
 	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 	"google.golang.org/grpc/test/bufconn"
 
 	"example/federation"
@@ -124,3 +126,69 @@ func TestFederation(t *testing.T) {
 		t.Errorf("(-got, +want)\n%s", diff)
 	}
 }
+
+func TestFederation_NoValue(t *testing.T) {
+	ctx := context.Background()
+	listener = bufconn.Listen(bufSize)
+
+	if os.Getenv("ENABLE_JAEGER") != "" {
+		exporter, err := otlptracegrpc.New(ctx, otlptracegrpc.WithInsecure())
+		if err != nil {
+			t.Fatal(err)
+		}
+		tp := sdktrace.NewTracerProvider(
+			sdktrace.WithBatcher(exporter),
+			sdktrace.WithResource(
+				resource.NewWithAttributes(
+					semconv.SchemaURL,
+					semconv.ServiceNameKey.String("example10/oneof"),
+					semconv.ServiceVersionKey.String("1.0.0"),
+					attribute.String("environment", "dev"),
+				),
+			),
+			sdktrace.WithSampler(sdktrace.AlwaysSample()),
+		)
+		defer tp.Shutdown(ctx)
+		otel.SetTextMapPropagator(propagation.TraceContext{})
+		otel.SetTracerProvider(tp)
+	}
+
+	conn, err := grpc.DialContext(ctx, "", grpc.WithContextDialer(dialer), grpc.WithInsecure())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+
+	userClient = user.NewUserServiceClient(conn)
+
+	grpcServer := grpc.NewServer()
+
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
+		Level: slog.LevelDebug,
+	}))
+	federationServer, err := federation.NewFederationService(federation.FederationServiceConfig{
+		Client: new(clientConfig),
+		Logger: logger,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	user.RegisterUserServiceServer(grpcServer, &UserServer{})
+	federation.RegisterFederationServiceServer(grpcServer, federationServer)
+
+	go func() {
+		if err := grpcServer.Serve(listener); err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	client := federation.NewFederationServiceClient(conn)
+	_, err = client.GetNoValue(ctx, &federation.GetNoValueRequest{})
+	if err == nil {
+		t.Fatal("unexpected error nil")
+	}
+	expectedErr := status.New(codes.Unknown, "NoValue is invalid field")
+	if diff := cmp.Diff(err.Error(), expectedErr.Err().Error()); diff != "" {
+		t.Errorf("(-got, +want)\n%s", diff)
+	}
+}
diff --git a/_examples/10_oneof/proto/federation/federation.proto b/_examples/10_oneof/proto/federation/federation.proto
index 241811cb..ac2b8a7e 100644
--- a/_examples/10_oneof/proto/federation/federation.proto
+++ b/_examples/10_oneof/proto/federation/federation.proto
@@ -13,6 +13,7 @@ option (grpc.federation.file)= {
 service FederationService {
   option (grpc.federation.service) = {};
   rpc Get(GetRequest) returns (GetResponse) {};
+  rpc GetNoValue(GetNoValueRequest) returns (GetNoValueResponse) {};
 }
 
 message GetRequest {}
@@ -32,6 +33,15 @@ message GetResponse {
   string msg = 2 [(grpc.federation.field).by = "msg_sel.message"];
 }
 
+message GetNoValueRequest {}
+
+message GetNoValueResponse {
+  option (grpc.federation.message) = {
+    def { name: "no_value_sel" message { name: "NoValueSelection" } }
+  };
+  M no_value = 1 [(grpc.federation.field).by = "no_value_sel.no_value"];
+}
+
 message UserSelection {
   oneof user {
     User user_a = 1 [
@@ -113,6 +123,23 @@ message MessageSelection {
   }
 }
 
+message NoValueSelection {
+  oneof no_value {
+    M m_a = 1 [
+      (grpc.federation.field).oneof = {
+        if: "false"
+        by: "M{value: 'a'}"
+      }
+    ];
+    M m_b = 2 [
+      (grpc.federation.field).oneof = {
+        if: "false"
+        by: "M{value: 'b'}"
+      }
+    ];
+  }
+}
+
 message M {
   string value = 1 [(grpc.federation.field).by = "'foo'"];
 }
diff --git a/grpc/federation/cel.go b/grpc/federation/cel.go
index 8dc6ca18..34c463ec 100644
--- a/grpc/federation/cel.go
+++ b/grpc/federation/cel.go
@@ -11,9 +11,13 @@ import (
 	"sync"
 
 	"github.com/google/cel-go/cel"
+	celast "github.com/google/cel-go/common/ast"
+	"github.com/google/cel-go/common/operators"
 	celtypes "github.com/google/cel-go/common/types"
 	"github.com/google/cel-go/common/types/ref"
+	"github.com/google/cel-go/parser"
 	"golang.org/x/sync/singleflight"
+	exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
 	"google.golang.org/genproto/googleapis/rpc/errdetails"
 	grpccodes "google.golang.org/grpc/codes"
 	grpcstatus "google.golang.org/grpc/status"
@@ -158,6 +162,10 @@ func NewOneofSelectorFieldType(typ *celtypes.Type, fieldName string, oneofTypes
 		}
 		field := rv.FieldByName(fieldName)
 		fieldImpl := reflect.ValueOf(field.Interface())
+		if !fieldImpl.IsValid() {
+			// prevent panic if no value assigned
+			return nil, fmt.Errorf("%s is invalid field", fieldName)
+		}
 		for idx, oneofType := range oneofTypes {
 			if fieldImpl.Type() != oneofType {
 				continue
@@ -731,6 +739,25 @@ func createCELAst(req *EvalCELRequest, env *cel.Env) (*cel.Ast, error) {
 	if iss.Err() != nil {
 		return nil, iss.Err()
 	}
+
+	checkedExpr, err := cel.AstToCheckedExpr(ast)
+	if err != nil {
+		return nil, err
+	}
+	if newComparingNullResolver().Resolve(checkedExpr) {
+		ca, err := celast.ToAST(checkedExpr)
+		if err != nil {
+			return nil, err
+		}
+		expr, err = parser.Unparse(ca.Expr(), ca.SourceInfo())
+		if err != nil {
+			return nil, err
+		}
+		ast, iss = env.Compile(expr)
+		if iss.Err() != nil {
+			return nil, iss.Err()
+		}
+	}
 	return ast, nil
 }
 
@@ -832,3 +859,173 @@ func SetCELValue[T any](ctx context.Context, param *SetCELValueParam[T]) error {
 	}
 	return nil
 }
+
+// comparingNullResolver is a feature that allows to compare typed null and null value correctly.
+// It parses the expression and wraps the message with grpc.federation.cast.null_value if the message is compared to null.
+type comparingNullResolver struct {
+	checkedExpr *exprpb.CheckedExpr
+	lastID      int64
+	resolved    bool
+}
+
+func newComparingNullResolver() *comparingNullResolver {
+	return &comparingNullResolver{}
+}
+
+func (r *comparingNullResolver) init(checkedExpr *exprpb.CheckedExpr) {
+	var lastID int64
+	for k := range checkedExpr.GetReferenceMap() {
+		if lastID < k {
+			lastID = k
+		}
+	}
+	for k := range checkedExpr.GetTypeMap() {
+		if lastID < k {
+			lastID = k
+		}
+	}
+	r.checkedExpr = checkedExpr
+	r.lastID = lastID
+	r.resolved = false
+}
+
+func (r *comparingNullResolver) nextID() int64 {
+	r.lastID++
+	return r.lastID
+}
+
+func (r *comparingNullResolver) Resolve(checkedExpr *exprpb.CheckedExpr) bool {
+	r.init(checkedExpr)
+	newExprVisitor().Visit(checkedExpr.GetExpr(), func(e *exprpb.Expr) {
+		switch e.GetExprKind().(type) {
+		case *exprpb.Expr_CallExpr:
+			r.resolveCallExpr(e)
+		}
+	})
+	return r.resolved
+}
+
+func (r *comparingNullResolver) resolveCallExpr(e *exprpb.Expr) {
+	target := r.lookupComparingNullCallExpr(e)
+	if target == nil {
+		return
+	}
+	newID := r.nextID()
+	newExprKind := &exprpb.Expr_CallExpr{
+		CallExpr: &exprpb.Expr_Call{
+			Function: grpcfedcel.CastNullValueFunc,
+			Args: []*exprpb.Expr{
+				{
+					Id:       target.GetId(),
+					ExprKind: target.GetExprKind(),
+				},
+			},
+		},
+	}
+	target.Id = newID
+	target.ExprKind = newExprKind
+	r.checkedExpr.GetReferenceMap()[newID] = &exprpb.Reference{
+		OverloadId: []string{grpcfedcel.CastNullValueFunc},
+	}
+	r.checkedExpr.GetTypeMap()[newID] = &exprpb.Type{
+		TypeKind: &exprpb.Type_Dyn{},
+	}
+	r.resolved = true
+}
+
+func (r *comparingNullResolver) lookupComparingNullCallExpr(e *exprpb.Expr) *exprpb.Expr {
+	call := e.GetCallExpr()
+	fnName := call.GetFunction()
+	if fnName == operators.Equals || fnName == operators.NotEquals {
+		lhs := call.GetArgs()[0]
+		rhs := call.GetArgs()[1]
+		var target *exprpb.Expr
+		if _, ok := lhs.GetConstExpr().GetConstantKind().(*exprpb.Constant_NullValue); ok {
+			target = rhs
+		}
+		if _, ok := rhs.GetConstExpr().GetConstantKind().(*exprpb.Constant_NullValue); ok {
+			if target != nil {
+				// maybe null == null
+				return nil
+			}
+			target = lhs
+		}
+		if target == nil {
+			return nil
+		}
+		if target.GetCallExpr() != nil && target.GetCallExpr().GetFunction() == grpcfedcel.CastNullValueFunc {
+			return nil
+		}
+		return target
+	}
+	return nil
+}
+
+type exprVisitor struct {
+	callback func(e *exprpb.Expr)
+}
+
+func newExprVisitor() *exprVisitor {
+	return &exprVisitor{}
+}
+
+func (v *exprVisitor) Visit(e *exprpb.Expr, cb func(e *exprpb.Expr)) {
+	v.callback = cb
+	v.visit(e)
+}
+
+func (v *exprVisitor) visit(e *exprpb.Expr) {
+	if e == nil {
+		return
+	}
+	v.callback(e)
+
+	switch e.GetExprKind().(type) {
+	case *exprpb.Expr_SelectExpr:
+		v.visitSelect(e)
+	case *exprpb.Expr_CallExpr:
+		v.visitCall(e)
+	case *exprpb.Expr_ListExpr:
+		v.visitList(e)
+	case *exprpb.Expr_StructExpr:
+		v.visitStruct(e)
+	case *exprpb.Expr_ComprehensionExpr:
+		v.visitComprehension(e)
+	}
+}
+
+func (v *exprVisitor) visitSelect(e *exprpb.Expr) {
+	sel := e.GetSelectExpr()
+	v.visit(sel.GetOperand())
+}
+
+func (v *exprVisitor) visitCall(e *exprpb.Expr) {
+	call := e.GetCallExpr()
+	for _, arg := range call.GetArgs() {
+		v.visit(arg)
+	}
+	v.visit(call.GetTarget())
+}
+
+func (v *exprVisitor) visitList(e *exprpb.Expr) {
+	l := e.GetListExpr()
+	for _, elem := range l.GetElements() {
+		v.visit(elem)
+	}
+}
+
+func (v *exprVisitor) visitStruct(e *exprpb.Expr) {
+	msg := e.GetStructExpr()
+	for _, ent := range msg.GetEntries() {
+		v.visit(ent.GetValue())
+	}
+}
+
+func (v *exprVisitor) visitComprehension(e *exprpb.Expr) {
+	comp := e.GetComprehensionExpr()
+	v.visit(comp.GetIterRange())
+	v.visit(comp.GetAccuInit())
+	v.visit(comp.GetLoopCondition())
+	v.visit(comp.GetLoopStep())
+	v.visit(comp.GetResult())
+}
diff --git a/grpc/federation/cel/bind.go b/grpc/federation/cel/bind.go
index 12e65d7a..030d404d 100644
--- a/grpc/federation/cel/bind.go
+++ b/grpc/federation/cel/bind.go
@@ -31,7 +31,12 @@ func BindFunction(name string, opts ...BindFunctionOpt) []cel.EnvOption {
 			if sel != "" {
 				fqdn = sel + "." + funcName
 			}
-			argsWithCtx := append([]ast.Expr{mef.NewIdent(ContextVariableName)}, args...)
+			var argsWithCtx []ast.Expr
+			if len(args) > 0 && args[0].AsIdent() == ContextVariableName {
+				argsWithCtx = args
+			} else {
+				argsWithCtx = append([]ast.Expr{mef.NewIdent(ContextVariableName)}, args...)
+			}
 			return mef.NewCall(fqdn, argsWithCtx...), nil
 		})),
 		cel.Function(name, celOpts...),
@@ -45,7 +50,12 @@ func BindMemberFunction(name string, opts ...BindMemberFunctionOpt) []cel.EnvOpt
 	}
 	return []cel.EnvOption{
 		cel.Macros(cel.ReceiverVarArgMacro(name, func(mef cel.MacroExprFactory, target ast.Expr, args []ast.Expr) (ast.Expr, *cel.Error) {
-			argsWithCtx := append([]ast.Expr{mef.NewIdent(ContextVariableName)}, args...)
+			var argsWithCtx []ast.Expr
+			if len(args) > 0 && args[0].AsIdent() == ContextVariableName {
+				argsWithCtx = args
+			} else {
+				argsWithCtx = append([]ast.Expr{mef.NewIdent(ContextVariableName)}, args...)
+			}
 			return mef.NewMemberCall(name, target, argsWithCtx...), nil
 		})),
 		cel.Function(name, celOpts...),
diff --git a/grpc/federation/cel/cast.go b/grpc/federation/cel/cast.go
new file mode 100644
index 00000000..caef67bc
--- /dev/null
+++ b/grpc/federation/cel/cast.go
@@ -0,0 +1,46 @@
+package cel
+
+import (
+	"reflect"
+
+	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/common/types"
+	"github.com/google/cel-go/common/types/ref"
+)
+
+const CastPackageName = "cast"
+
+const (
+	CastNullValueFunc = "grpc.federation.cast.null_value"
+)
+
+type CastLibrary struct{}
+
+func (lib *CastLibrary) LibraryName() string {
+	return CastPackageName
+}
+
+func (lib *CastLibrary) CompileOptions() []cel.EnvOption {
+	opts := []cel.EnvOption{
+		cel.OptionalTypes(),
+		cel.Function(CastNullValueFunc,
+			cel.Overload("grpc_federation_cast_null_value",
+				[]*cel.Type{cel.DynType}, cel.DynType,
+				cel.UnaryBinding(lib.nullValue),
+			),
+		),
+	}
+	return opts
+}
+
+func (lib *CastLibrary) ProgramOptions() []cel.ProgramOption {
+	return []cel.ProgramOption{}
+}
+
+func (lib *CastLibrary) nullValue(val ref.Val) ref.Val {
+	rv := reflect.ValueOf(val.Value())
+	if val.Value() == nil || val.Equal(types.NullValue) == types.True || rv.Kind() == reflect.Ptr && rv.IsNil() {
+		return types.NullValue
+	}
+	return val
+}
diff --git a/grpc/federation/cel/cast_test.go b/grpc/federation/cel/cast_test.go
new file mode 100644
index 00000000..728cfad0
--- /dev/null
+++ b/grpc/federation/cel/cast_test.go
@@ -0,0 +1,75 @@
+package cel_test
+
+import (
+	"testing"
+
+	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/common/types"
+	"github.com/google/cel-go/common/types/ref"
+
+	cellib "github.com/mercari/grpc-federation/grpc/federation/cel"
+	"github.com/mercari/grpc-federation/grpc/federation/cel/testdata/testpb"
+)
+
+func TestCast(t *testing.T) {
+	tests := []struct {
+		name     string
+		expr     string
+		msg      any
+		expected ref.Val
+	}{
+		{
+			name:     "cast nil",
+			expr:     "grpc.federation.cast.null_value(msg) == null",
+			msg:      nil,
+			expected: types.True,
+		},
+		{
+			name:     "cast typed-nil",
+			expr:     "grpc.federation.cast.null_value(msg) == null",
+			msg:      (*testpb.Message)(nil),
+			expected: types.True,
+		},
+		{
+			name:     "cast struct pointer",
+			expr:     "grpc.federation.cast.null_value(msg) == null",
+			msg:      &testpb.Message{},
+			expected: types.False,
+		},
+		{
+			name:     "cast lit",
+			expr:     "grpc.federation.cast.null_value(msg) == null",
+			msg:      100,
+			expected: types.False,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			env, err := cel.NewEnv(
+				cel.Types(&testpb.Message{}),
+				cel.Lib(new(cellib.CastLibrary)),
+				cel.Variable("msg", cel.DynType),
+			)
+			if err != nil {
+				t.Fatal(err)
+			}
+			ast, iss := env.Compile(test.expr)
+			if iss.Err() != nil {
+				t.Fatal(iss.Err())
+			}
+			program, err := env.Program(ast)
+			if err != nil {
+				t.Fatal(err)
+			}
+			out, _, err := program.Eval(map[string]any{
+				"msg": test.msg,
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if out.Equal(test.expected) == types.False {
+				t.Fatalf("unexpected value: want %v but got %v", test.expected, out)
+			}
+		})
+	}
+}
diff --git a/grpc/federation/cel/lib.go b/grpc/federation/cel/lib.go
index 27359fc3..da6d74b2 100644
--- a/grpc/federation/cel/lib.go
+++ b/grpc/federation/cel/lib.go
@@ -25,6 +25,7 @@ func NewLibrary(typeAdapter types.Adapter) *Library {
 			new(EnumLibrary),
 			mdLib,
 			logLib,
+			new(CastLibrary),
 		},
 	}
 }