diff --git a/src/ppx/ppx_common.ml b/src/ppx/ppx_common.ml
index ef5ecfb..051bc19 100644
--- a/src/ppx/ppx_common.ml
+++ b/src/ppx/ppx_common.ml
@@ -11,17 +11,6 @@
 open Ppxlib
 open Ast_builder.Default
 
-let str_of_expr e = Pprintast.string_of_expression e
-let str_of_pat p =
-  Pprintast.pattern Format.str_formatter p;
-  Format.flush_str_formatter ()
-let str_of_structure e = Pprintast.string_of_structure e
-
-let llid ~loc s = {txt=Longident.parse s; loc}
-let esome e =
-  let loc = e.pexp_loc in
-  pexp_construct ~loc (llid ~loc "Some") (Some e)
-
 (** service *)
 
 type options = {
@@ -45,6 +34,46 @@ type options = {
   service : expression option;
 }
 
+let loc = !Ast_helper.default_loc
+let global_errors = ref [%expr None]
+let global_error_type = ref [%type: exn]
+let global_security = ref [%expr None]
+let global_security_type = ref [%type: EzAPI.no_security]
+
+let remove_poly c = match c.ptyp_desc with
+  | Ptyp_poly ([], c) -> c
+  | _ -> c
+
+let remove_constraint e = match e.pexp_desc with
+  | Pexp_constraint (e, _) -> e
+  | _ -> e
+
+let extract_list_type = function
+  | None -> [%type: _]
+  | Some t ->
+    let t = remove_poly t in
+    match t.ptyp_desc with
+    | Ptyp_constr ({txt=(Lident "list" | Ldot (Lident "List", "t")); _}, [ c ]) -> c
+    | _ -> t
+
+let set_global_errors ?typ e =
+  let loc = e.pexp_loc in
+  global_errors := [%expr Some [%e remove_constraint e]];
+  global_error_type := extract_list_type typ
+
+let set_global_security ?typ e =
+  let loc = e.pexp_loc in
+  global_security := [%expr Some [%e remove_constraint e]];
+  global_security_type := extract_list_type typ
+
+let set_globals l =
+  List.iter (fun ({txt; _}, e) ->
+      let name = Longident.name txt in
+      match name with
+      | "errors" -> set_global_errors e
+      | "security" -> set_global_security e
+      | _ -> ()) l
+
 let raw e =
   let loc = e.pexp_loc in
   [%expr EzAPI.Raw (List.filter_map EzAPI.Mime.parse [%e e])]
@@ -53,11 +82,11 @@ let options loc = {
   path = [%expr EzAPI.Path.root];
   input = [%expr EzAPI.Empty];
   output = [%expr EzAPI.Empty];
-  errors = [%expr None]; params = [%expr None];
+  errors = !global_errors; params = [%expr None];
   section = [%expr None]; name=[%expr None]; descr = [%expr None];
-  security = [%expr None]; register=[%expr true]; input_example = [%expr None];
-  hide = [%expr None]; output_example = [%expr None]; error_type = [%type: exn];
-  security_type = [%type: EzAPI.no_security];
+  security = !global_security; register=[%expr true]; input_example = [%expr None];
+  hide = [%expr None]; output_example = [%expr None]; error_type = !global_error_type;
+  security_type = !global_security_type;
   debug = false; directory = None; service = None
 }
 
@@ -75,7 +104,7 @@ let parse_arg ~loc s = match String.index_opt s ':' with
       Location.raise_errorf ~loc "argument type not understood: %S" typ
 
 let parse_path ~loc s =
-  let path ~loc s = pexp_ident ~loc (llid ~loc ("EzAPI.Path." ^ s)) in
+  let path ~loc s = pexp_ident ~loc {txt=Longident.parse ("EzAPI.Path." ^ s); loc} in
   let l = String.split_on_char '/' s in
   let l = List.filter (fun s -> s <> "") l in
   List.fold_left (fun acc s ->
@@ -107,15 +136,15 @@ let get_options ~loc ?(options=options loc) ?name p =
         | "raw_input" -> name, { acc with input = raw e }
         | "output" -> name, { acc with output = [%expr EzAPI.Json [%e e]] }
         | "raw_output" -> name, { acc with output = raw e }
-        | "params" -> name, { acc with params = esome e }
-        | "errors" -> name, { acc with errors = esome e; error_type = ptyp_any ~loc }
-        | "section" -> name, { acc with section = esome e }
+        | "params" -> name, { acc with params = [%expr Some [%e e]] }
+        | "errors" -> name, { acc with errors = [%expr Some [%e e]]; error_type = [%type: _] }
+        | "section" -> name, { acc with section = [%expr Some [%e e]] }
         | "name" ->
           begin match e.pexp_desc with
             | Pexp_constant cst ->
               begin match name, string_literal cst with
-                | None, Some s -> Some s,  { acc with name = esome e }
-                | Some n, _ -> Some n, { acc with name = esome e }
+                | None, Some s -> Some s,  { acc with name = [%expr Some [%e e]] }
+                | Some n, _ -> Some n, { acc with name = [%expr Some [%e e]] }
                 | _ -> Format.eprintf "name should be a string literal"; name, acc
               end
             | _ ->
@@ -123,12 +152,12 @@ let get_options ~loc ?(options=options loc) ?name p =
               | Some n -> Some n, { acc with name = [%expr Some [%e estring ~loc n]] }
               | _ -> name, acc
           end
-        | "descr" -> name, { acc with descr = esome e }
-        | "security" -> name, { acc with security = esome e; security_type = ptyp_any ~loc }
+        | "descr" -> name, { acc with descr = [%expr Some [%e e]] }
+        | "security" -> name, { acc with security = [%expr Some [%e e]]; security_type = [%type: _] }
         | "register" -> name, { acc with register = e }
         | "hide" -> name, { acc with hide = e }
-        | "input_example" -> name, { acc with input_example = esome e }
-        | "output_example" -> name, { acc with output_example = esome e }
+        | "input_example" -> name, { acc with input_example = [%expr Some [%e e]] }
+        | "output_example" -> name, { acc with output_example = [%expr Some [%e e]] }
         | "debug" -> name, { acc with debug = true }
         | "dir" -> begin match e.pexp_desc with
             | Pexp_constant cst ->
@@ -139,10 +168,10 @@ let get_options ~loc ?(options=options loc) ?name p =
             | _ -> Format.eprintf "directory should be a literal"; name, acc
           end
         | "service" ->
-          name, { acc with service = Some e; error_type = ptyp_any ~loc; security_type = ptyp_any ~loc }
+          name, { acc with service = Some e; error_type = [%type: _]; security_type = [%type: _] }
         | _ -> name, acc) (name, options) l
   | PStr [ {pstr_desc=Pstr_eval ({pexp_desc=Pexp_ident _; _} as e, _); _} ] ->
-    name, { options with service = Some e; error_type = ptyp_any ~loc; security_type = ptyp_any ~loc }
+    name, { options with service = Some e; error_type = [%type: _]; security_type = [%type: _] }
   | PStr [ {pstr_desc=Pstr_eval ({pexp_desc=Pexp_constant Pconst_string (s, loc, _); _}, _); _} ] ->
     name, { options with path = parse_path ~loc s }
   | PStr s ->
@@ -173,11 +202,9 @@ let service_value ?name ?options ~meth ~loc p =
         Optional "output_example", options.output_example;
         Nolabel, options.path ] in
     let pat = ppat_constraint ~loc (pvar ~loc name) @@
-      ptyp_constr ~loc (llid ~loc "EzAPI.service") [
-        ptyp_any ~loc; ptyp_any ~loc; ptyp_any ~loc; options.error_type;
-        options.security_type ] in
+      [%type: (_, _, _, [%t options.error_type], [%t options.security_type]) EzAPI.service] in
     let str = pstr_value ~loc Nonrecursive [ value_binding ~loc ~pat ~expr ] in
-    if options.debug then Format.printf "%s@." @@ str_of_structure [ str ];
+    if options.debug then Format.printf "%a@." Pprintast.structure_item str;
     str, name, options
 
 (** register service/handler *)
@@ -205,7 +232,7 @@ let register name a =
         ~expr:(eapply ~loc (evar ~loc "EzAPIServerUtils.register") [
             e; evar ~loc name; evar ~loc ppx_dir_name ]) in
     let str = ppx_dir @ [ pstr_value ~loc Nonrecursive [ register ] ] in
-    if options.debug then Format.printf "%s@." @@ str_of_structure str;
+    if options.debug then Format.printf "%a@." Pprintast.structure str;
     str
 
 let register_ws ~onclose react_name bg_name a =
@@ -215,7 +242,7 @@ let register_ws ~onclose react_name bg_name a =
   let ppx_dir_name = match options.directory with None -> "ppx_dir" | Some s -> s in
   let onclose = match onclose with
     | [] -> [%expr None]
-    | [ {pvb_pat = {ppat_desc = Ppat_var {txt; loc}; _}; _} ] -> esome (evar ~loc txt)
+    | [ {pvb_pat = {ppat_desc = Ppat_var {txt; loc}; _}; _} ] -> [%expr Some [%e evar ~loc txt]]
     | _ -> Location.raise_errorf ~loc "too many value bindings" in
   match options.service with
   | None -> Location.raise_errorf ~loc "service not defined"
@@ -229,7 +256,7 @@ let register_ws ~onclose react_name bg_name a =
             Labelled "bg", evar ~loc bg_name;
             Nolabel, evar ~loc ppx_dir_name ]) in
     let str = ppx_dir @ [ pstr_value ~loc Nonrecursive [ register ] ] in
-    if options.debug then Format.printf "%s@." @@ str_of_structure str;
+    if options.debug then Format.printf "%a@." Pprintast.structure str;
     str
 
 let process name a =
@@ -243,7 +270,7 @@ let process name a =
       value_binding ~loc ~pat:(pvar ~loc ppx_dir_name)
         ~expr:(eapply ~loc (evar ~loc "EzAPIServerUtils.register") [
             evar ~loc service_name; evar ~loc name; evar ~loc ppx_dir_name ]) ] in
-  if options.debug then Format.printf "%s@." @@ str_of_structure [ register ];
+  if options.debug then Format.printf "%a@." Pprintast.structure_item register;
   ppx_dir @ [ service; register ]
 
 let process_ws ~onclose react_name bg_name a =
@@ -255,7 +282,7 @@ let process_ws ~onclose react_name bg_name a =
   let ppx_dir_name = match options.directory with None -> "ppx_dir" | Some s -> s in
   let onclose = match onclose with
     | [] -> [%expr None]
-    | [ {pvb_pat = {ppat_desc = Ppat_var {txt; loc}; _}; _} ] -> esome (evar ~loc txt)
+    | [ {pvb_pat = {ppat_desc = Ppat_var {txt; loc}; _}; _} ] -> [%expr Some [%e evar ~loc txt]]
     | _ -> Location.raise_errorf ~loc "too many value bindings" in
   let register =
     pstr_value ~loc Nonrecursive [
@@ -266,7 +293,7 @@ let process_ws ~onclose react_name bg_name a =
             Labelled "react", evar ~loc react_name;
             Labelled "bg", evar ~loc bg_name;
             Nolabel, evar ~loc ppx_dir_name ]) ] in
-  if options.debug then Format.printf "%s@." @@ str_of_structure [ register ];
+  if options.debug then Format.printf "%a@." Pprintast.structure_item register;
   ppx_dir @ [ service; register ]
 
 let handler_args e =
@@ -308,11 +335,11 @@ let server_options e =
     List.fold_left (fun acc (s, e) -> match s with
         | "port" -> { acc with port = e }
         | "dir" -> { acc with dir = e }
-        | "catch" -> { acc with catch = esome e }
-        | "headers" -> { acc with allow_headers = esome e }
-        | "methods" -> { acc with allow_methods = esome e }
-        | "origin" -> { acc with allow_origin = esome e }
-        | "credentials" -> { acc with allow_credentials = esome e }
+        | "catch" -> { acc with catch = [%expr Some [%e e]] }
+        | "headers" -> { acc with allow_headers = [%expr Some [%e e]] }
+        | "methods" -> { acc with allow_methods = [%expr Some [%e e]] }
+        | "origin" -> { acc with allow_origin = [%expr Some [%e e]] }
+        | "credentials" -> { acc with allow_credentials = [%expr Some [%e e]] }
         | _ -> acc) (dft (eint ~loc 8080)) l
   | _ -> Location.raise_errorf ~loc "server options not understood"
 
@@ -322,12 +349,10 @@ let server_aux e =
   [%expr
     EzAPIServer.server ?catch:[%e options.catch] ?allow_headers:[%e options.allow_headers]
       ?allow_methods:[%e options.allow_methods] ?allow_origin:[%e options.allow_origin]
-      ?allow_credentials:[%e options.allow_credentials]
-      [%e elist ~loc [
-          pexp_tuple ~loc [
-            options.port;
-            pexp_construct ~loc (llid ~loc "EzAPIServerUtils.API") (Some options.dir)
-          ] ] ] ]
+      ?allow_credentials:[%e options.allow_credentials] [
+      ([%e options.port], EzAPIServerUtils.API [%e options.dir])
+    ]
+  ]
 
 let server ~loc p =
   match p with
@@ -447,6 +472,22 @@ let transform ?kind () =
             let options = { (options loc) with register = [%expr false] } in
             let service, _, _ = service_value ~options ~meth:txt ~loc p in
             service :: acc
+          (* globals *)
+          | Pstr_extension (({txt="service"; _}, PStr [ {pstr_desc=Pstr_eval ({pexp_desc=Pexp_record (l, _); _}, _); _} ]), _) ->
+            set_globals l;
+            acc
+          | Pstr_extension (({txt="service"; _}, PStr [ {pstr_desc=Pstr_value (_, l); _} ]), _) ->
+            List.iter (fun vb ->
+                match vb.pvb_pat.ppat_desc with
+                | Ppat_var {txt="errors"; _} -> set_global_errors vb.pvb_expr
+                | Ppat_var {txt="security"; _} -> set_global_security vb.pvb_expr
+                | Ppat_constraint ({ppat_desc = Ppat_var {txt="errors"; _}; _}, typ) ->
+                  set_global_errors ~typ vb.pvb_expr
+                | Ppat_constraint ({ppat_desc = Ppat_var {txt="security"; _}; _}, typ) ->
+                  set_global_security ~typ vb.pvb_expr
+                | _ -> ()) l;
+            acc
+          (* service deriver *)
           | Pstr_type (_rec_flag, [ t ]) ->
             let loc = t.ptype_loc in
             begin match List.find_opt (fun a -> List.mem a.attr_name.txt methods) t.ptype_attributes with
diff --git a/test/ppx/test_ppx_lib.ml b/test/ppx/test_ppx_lib.ml
index 5d79a45..74dae2e 100644
--- a/test/ppx/test_ppx_lib.ml
+++ b/test/ppx/test_ppx_lib.ml
@@ -1,9 +1,20 @@
+
+type error = {
+  name: string;
+  msg: string;
+} [@@deriving encoding]
+
+let%service errors = [
+  EzAPI.Err.make ~code:400 ~name:"Error" ~encoding:error_enc ~select:Option.some ~deselect:Fun.id
+]
+and security : EzAPI.Security.bearer list = [ `Bearer {EzAPI.Security.bearer_name="Bearer"; format=None} ]
+
 type nonrec test_derive_input = {
   foo: string;
   bar: int;
 }
 and test_derive_output = int
-[@@post {path="/test/getter"; debug}]
+[@@post {path="/test/getter"}]
 
 let%post echo_input = {
   path="/echo_input"; raw_input=["text/plain"];