diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 80b61edd3657a..67c7fb2634353 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7316,8 +7316,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         if (propertySymbol.flags & SymbolFlags.Prototype) {
                             continue;
                         }
-                        if (getDeclarationModifierFlagsFromSymbol(propertySymbol) & (ModifierFlags.Private | ModifierFlags.Protected) && context.tracker.reportPrivateInBaseOfClassExpression) {
-                            context.tracker.reportPrivateInBaseOfClassExpression(unescapeLeadingUnderscores(propertySymbol.escapedName));
+                        if ((getDeclarationModifierFlagsFromSymbol(propertySymbol) & (ModifierFlags.Private | ModifierFlags.Protected) || propertySymbol.valueDeclaration && isPrivateIdentifierClassElementDeclaration(propertySymbol.valueDeclaration)) && context.tracker.reportPrivateInBaseOfClassExpression) {
+                            context.tracker.reportPrivateInBaseOfClassExpression(symbolToString(propertySymbol));
                         }
                     }
                     if (checkTruncationLength(context) && (i + 2 < properties.length - 1)) {
diff --git a/tests/baselines/reference/declarationEmitMixinPrivateField1.errors.txt b/tests/baselines/reference/declarationEmitMixinPrivateField1.errors.txt
new file mode 100644
index 0000000000000..c7ddfa5e088c7
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitMixinPrivateField1.errors.txt
@@ -0,0 +1,30 @@
+another.ts(7,1): error TS4094: Property '#onDispose' of exported anonymous class type may not be private or protected.
+first.ts(7,1): error TS4094: Property '#onDispose' of exported anonymous class type may not be private or protected.
+first.ts(8,14): error TS4094: Property '#onDispose' of exported anonymous class type may not be private or protected.
+
+
+==== first.ts (2 errors) ====
+    declare function mix<TMix>(mixin: TMix): TMix;
+    
+    const DisposableMixin = class {
+        #onDispose() {}
+    };
+    
+    export default mix(DisposableMixin);
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS4094: Property '#onDispose' of exported anonymous class type may not be private or protected.
+    export class Monitor extends mix(DisposableMixin) {}
+                 ~~~~~~~
+!!! error TS4094: Property '#onDispose' of exported anonymous class type may not be private or protected.
+    
+==== another.ts (1 errors) ====
+    declare function mix<TMix>(mixin: TMix): TMix;
+    
+    const DisposableMixin = class {
+        #onDispose() {}
+    };
+    
+    export default class extends mix(DisposableMixin) {}
+    ~~~~~~
+!!! error TS4094: Property '#onDispose' of exported anonymous class type may not be private or protected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationEmitMixinPrivateField1.js b/tests/baselines/reference/declarationEmitMixinPrivateField1.js
new file mode 100644
index 0000000000000..86eba3f5e5bf1
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitMixinPrivateField1.js
@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/declarationEmitMixinPrivateField1.ts] ////
+
+//// [first.ts]
+declare function mix<TMix>(mixin: TMix): TMix;
+
+const DisposableMixin = class {
+    #onDispose() {}
+};
+
+export default mix(DisposableMixin);
+export class Monitor extends mix(DisposableMixin) {}
+
+//// [another.ts]
+declare function mix<TMix>(mixin: TMix): TMix;
+
+const DisposableMixin = class {
+    #onDispose() {}
+};
+
+export default class extends mix(DisposableMixin) {}
+
+
+//// [first.js]
+const DisposableMixin = class {
+    #onDispose() { }
+};
+export default mix(DisposableMixin);
+export class Monitor extends mix(DisposableMixin) {
+}
+//// [another.js]
+const DisposableMixin = class {
+    #onDispose() { }
+};
+export default class extends mix(DisposableMixin) {
+}
diff --git a/tests/baselines/reference/declarationEmitMixinPrivateField1.symbols b/tests/baselines/reference/declarationEmitMixinPrivateField1.symbols
new file mode 100644
index 0000000000000..c8f54a8419421
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitMixinPrivateField1.symbols
@@ -0,0 +1,47 @@
+//// [tests/cases/compiler/declarationEmitMixinPrivateField1.ts] ////
+
+=== first.ts ===
+declare function mix<TMix>(mixin: TMix): TMix;
+>mix : Symbol(mix, Decl(first.ts, 0, 0))
+>TMix : Symbol(TMix, Decl(first.ts, 0, 21))
+>mixin : Symbol(mixin, Decl(first.ts, 0, 27))
+>TMix : Symbol(TMix, Decl(first.ts, 0, 21))
+>TMix : Symbol(TMix, Decl(first.ts, 0, 21))
+
+const DisposableMixin = class {
+>DisposableMixin : Symbol(DisposableMixin, Decl(first.ts, 2, 5))
+
+    #onDispose() {}
+>#onDispose : Symbol(DisposableMixin.#onDispose, Decl(first.ts, 2, 31))
+
+};
+
+export default mix(DisposableMixin);
+>mix : Symbol(mix, Decl(first.ts, 0, 0))
+>DisposableMixin : Symbol(DisposableMixin, Decl(first.ts, 2, 5))
+
+export class Monitor extends mix(DisposableMixin) {}
+>Monitor : Symbol(Monitor, Decl(first.ts, 6, 36))
+>mix : Symbol(mix, Decl(first.ts, 0, 0))
+>DisposableMixin : Symbol(DisposableMixin, Decl(first.ts, 2, 5))
+
+=== another.ts ===
+declare function mix<TMix>(mixin: TMix): TMix;
+>mix : Symbol(mix, Decl(another.ts, 0, 0))
+>TMix : Symbol(TMix, Decl(another.ts, 0, 21))
+>mixin : Symbol(mixin, Decl(another.ts, 0, 27))
+>TMix : Symbol(TMix, Decl(another.ts, 0, 21))
+>TMix : Symbol(TMix, Decl(another.ts, 0, 21))
+
+const DisposableMixin = class {
+>DisposableMixin : Symbol(DisposableMixin, Decl(another.ts, 2, 5))
+
+    #onDispose() {}
+>#onDispose : Symbol(DisposableMixin.#onDispose, Decl(another.ts, 2, 31))
+
+};
+
+export default class extends mix(DisposableMixin) {}
+>mix : Symbol(mix, Decl(another.ts, 0, 0))
+>DisposableMixin : Symbol(DisposableMixin, Decl(another.ts, 2, 5))
+
diff --git a/tests/baselines/reference/declarationEmitMixinPrivateField1.types b/tests/baselines/reference/declarationEmitMixinPrivateField1.types
new file mode 100644
index 0000000000000..7e505b724a975
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitMixinPrivateField1.types
@@ -0,0 +1,66 @@
+//// [tests/cases/compiler/declarationEmitMixinPrivateField1.ts] ////
+
+=== first.ts ===
+declare function mix<TMix>(mixin: TMix): TMix;
+>mix : <TMix>(mixin: TMix) => TMix
+>    : ^    ^^     ^^    ^^^^^    
+>mixin : TMix
+>      : ^^^^
+
+const DisposableMixin = class {
+>DisposableMixin : typeof DisposableMixin
+>                : ^^^^^^^^^^^^^^^^^^^^^^
+>class {    #onDispose() {}} : typeof DisposableMixin
+>                            : ^^^^^^^^^^^^^^^^^^^^^^
+
+    #onDispose() {}
+>#onDispose : () => void
+>           : ^^^^^^^^^^
+
+};
+
+export default mix(DisposableMixin);
+>mix(DisposableMixin) : typeof DisposableMixin
+>                     : ^^^^^^^^^^^^^^^^^^^^^^
+>mix : <TMix>(mixin: TMix) => TMix
+>    : ^    ^^     ^^    ^^^^^    
+>DisposableMixin : typeof DisposableMixin
+>                : ^^^^^^^^^^^^^^^^^^^^^^
+
+export class Monitor extends mix(DisposableMixin) {}
+>Monitor : Monitor
+>        : ^^^^^^^
+>mix(DisposableMixin) : DisposableMixin
+>                     : ^^^^^^^^^^^^^^^
+>mix : <TMix>(mixin: TMix) => TMix
+>    : ^    ^^     ^^    ^^^^^    
+>DisposableMixin : typeof DisposableMixin
+>                : ^^^^^^^^^^^^^^^^^^^^^^
+
+=== another.ts ===
+declare function mix<TMix>(mixin: TMix): TMix;
+>mix : <TMix>(mixin: TMix) => TMix
+>    : ^    ^^     ^^    ^^^^^    
+>mixin : TMix
+>      : ^^^^
+
+const DisposableMixin = class {
+>DisposableMixin : typeof DisposableMixin
+>                : ^^^^^^^^^^^^^^^^^^^^^^
+>class {    #onDispose() {}} : typeof DisposableMixin
+>                            : ^^^^^^^^^^^^^^^^^^^^^^
+
+    #onDispose() {}
+>#onDispose : () => void
+>           : ^^^^^^^^^^
+
+};
+
+export default class extends mix(DisposableMixin) {}
+>mix(DisposableMixin) : DisposableMixin
+>                     : ^^^^^^^^^^^^^^^
+>mix : <TMix>(mixin: TMix) => TMix
+>    : ^    ^^     ^^    ^^^^^    
+>DisposableMixin : typeof DisposableMixin
+>                : ^^^^^^^^^^^^^^^^^^^^^^
+
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.errors.txt b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.errors.txt
index e755cfdfa259b..bd1a2fbb10cc0 100644
--- a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.errors.txt
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.errors.txt
@@ -2,9 +2,10 @@ emitClassExpressionInDeclarationFile2.ts(1,12): error TS4094: Property 'p' of ex
 emitClassExpressionInDeclarationFile2.ts(1,12): error TS4094: Property 'ps' of exported anonymous class type may not be private or protected.
 emitClassExpressionInDeclarationFile2.ts(16,17): error TS4094: Property 'property' of exported anonymous class type may not be private or protected.
 emitClassExpressionInDeclarationFile2.ts(23,14): error TS4094: Property 'property' of exported anonymous class type may not be private or protected.
+emitClassExpressionInDeclarationFile2.ts(31,3): error TS4094: Property 'prop' of exported anonymous class type may not be private or protected.
 
 
-==== emitClassExpressionInDeclarationFile2.ts (4 errors) ====
+==== emitClassExpressionInDeclarationFile2.ts (5 errors) ====
     export var noPrivates = class {
                ~~~~~~~~~~
 !!! error TS4094: Property 'p' of exported anonymous class type may not be private or protected.
@@ -43,4 +44,12 @@ emitClassExpressionInDeclarationFile2.ts(23,14): error TS4094: Property 'propert
     
     Test.getTags()
     test.tags();
+    
+    export class Test2 {
+      nested = class {
+      ~~~~~~
+!!! error TS4094: Property 'prop' of exported anonymous class type may not be private or protected.
+        private prop = 42;
+      }
+    }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.js b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.js
index 7448d7496af59..7232fe1224364 100644
--- a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.js
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.js
@@ -29,6 +29,12 @@ const test = new Test();
 
 Test.getTags()
 test.tags();
+
+export class Test2 {
+  nested = class {
+    private prop = 42;
+  }
+}
 
 
 //// [emitClassExpressionInDeclarationFile2.js]
@@ -54,7 +60,7 @@ var __setFunctionName = (this && this.__setFunctionName) || function (f, name, p
 };
 var _a;
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.Test = exports.FooItem = exports.noPrivates = void 0;
+exports.Test2 = exports.Test = exports.FooItem = exports.noPrivates = void 0;
 exports.WithTags = WithTags;
 exports.noPrivates = (_a = /** @class */ (function () {
         function class_1() {
@@ -98,3 +104,15 @@ exports.Test = Test;
 var test = new Test();
 Test.getTags();
 test.tags();
+var Test2 = /** @class */ (function () {
+    function Test2() {
+        this.nested = /** @class */ (function () {
+            function class_3() {
+                this.prop = 42;
+            }
+            return class_3;
+        }());
+    }
+    return Test2;
+}());
+exports.Test2 = Test2;
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.symbols b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.symbols
index 167ec73bdbabc..086e3075444cd 100644
--- a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.symbols
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.symbols
@@ -75,3 +75,14 @@ test.tags();
 >test : Symbol(test, Decl(emitClassExpressionInDeclarationFile2.ts, 24, 5))
 >tags : Symbol((Anonymous class).tags, Decl(emitClassExpressionInDeclarationFile2.ts, 17, 34))
 
+export class Test2 {
+>Test2 : Symbol(Test2, Decl(emitClassExpressionInDeclarationFile2.ts, 27, 12))
+
+  nested = class {
+>nested : Symbol(Test2.nested, Decl(emitClassExpressionInDeclarationFile2.ts, 29, 20))
+
+    private prop = 42;
+>prop : Symbol((Anonymous class).prop, Decl(emitClassExpressionInDeclarationFile2.ts, 30, 18))
+  }
+}
+
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.types b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.types
index b0365b56e6053..f4cc7ec5c4ad4 100644
--- a/tests/baselines/reference/emitClassExpressionInDeclarationFile2.types
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile2.types
@@ -116,3 +116,21 @@ test.tags();
 >tags : () => void
 >     : ^^^^^^    
 
+export class Test2 {
+>Test2 : Test2
+>      : ^^^^^
+
+  nested = class {
+>nested : typeof (Anonymous class)
+>       : ^^^^^^^^^^^^^^^^^^^^^^^^
+>class {    private prop = 42;  } : typeof (Anonymous class)
+>                                 : ^^^^^^^^^^^^^^^^^^^^^^^^
+
+    private prop = 42;
+>prop : number
+>     : ^^^^^^
+>42 : 42
+>   : ^^
+  }
+}
+
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile3.errors.txt b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.errors.txt
new file mode 100644
index 0000000000000..ec0e87b9aa6e2
--- /dev/null
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.errors.txt
@@ -0,0 +1,49 @@
+emitClassExpressionInDeclarationFile3.ts(1,12): error TS4094: Property '#p' of exported anonymous class type may not be private or protected.
+emitClassExpressionInDeclarationFile3.ts(1,12): error TS4094: Property '#ps' of exported anonymous class type may not be private or protected.
+emitClassExpressionInDeclarationFile3.ts(15,17): error TS4094: Property '#property' of exported anonymous class type may not be private or protected.
+emitClassExpressionInDeclarationFile3.ts(22,14): error TS4094: Property '#property' of exported anonymous class type may not be private or protected.
+emitClassExpressionInDeclarationFile3.ts(25,3): error TS4094: Property '#prop' of exported anonymous class type may not be private or protected.
+
+
+==== emitClassExpressionInDeclarationFile3.ts (5 errors) ====
+    export var noPrivates = class {
+               ~~~~~~~~~~
+!!! error TS4094: Property '#p' of exported anonymous class type may not be private or protected.
+!!! related TS9027 emitClassExpressionInDeclarationFile3.ts:1:12: Add a type annotation to the variable noPrivates.
+               ~~~~~~~~~~
+!!! error TS4094: Property '#ps' of exported anonymous class type may not be private or protected.
+!!! related TS9027 emitClassExpressionInDeclarationFile3.ts:1:12: Add a type annotation to the variable noPrivates.
+        static getTags() { }
+        tags() { }
+        static #ps = -1
+        #p = 12
+    }
+    
+    export class FooItem {
+        foo(): void { }
+        name?: string;
+        #property = "capitalism"
+    }
+    
+    export type Constructor<T> = new(...args: any[]) => T;
+    export function WithTags<T extends Constructor<FooItem>>(Base: T) {
+                    ~~~~~~~~
+!!! error TS4094: Property '#property' of exported anonymous class type may not be private or protected.
+        return class extends Base {
+            static getTags(): void { }
+            tags(): void { }
+        }
+    }
+    
+    export class Test extends WithTags(FooItem) {}
+                 ~~~~
+!!! error TS4094: Property '#property' of exported anonymous class type may not be private or protected.
+    
+    export class Test2 {
+      nested = class {
+      ~~~~~~
+!!! error TS4094: Property '#prop' of exported anonymous class type may not be private or protected.
+        #prop = 42;
+      }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile3.js b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.js
new file mode 100644
index 0000000000000..75fd92209ca14
--- /dev/null
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.js
@@ -0,0 +1,58 @@
+//// [tests/cases/compiler/emitClassExpressionInDeclarationFile3.ts] ////
+
+//// [emitClassExpressionInDeclarationFile3.ts]
+export var noPrivates = class {
+    static getTags() { }
+    tags() { }
+    static #ps = -1
+    #p = 12
+}
+
+export class FooItem {
+    foo(): void { }
+    name?: string;
+    #property = "capitalism"
+}
+
+export type Constructor<T> = new(...args: any[]) => T;
+export function WithTags<T extends Constructor<FooItem>>(Base: T) {
+    return class extends Base {
+        static getTags(): void { }
+        tags(): void { }
+    }
+}
+
+export class Test extends WithTags(FooItem) {}
+
+export class Test2 {
+  nested = class {
+    #prop = 42;
+  }
+}
+
+
+//// [emitClassExpressionInDeclarationFile3.js]
+export var noPrivates = class {
+    static getTags() { }
+    tags() { }
+    static #ps = -1;
+    #p = 12;
+};
+export class FooItem {
+    foo() { }
+    name;
+    #property = "capitalism";
+}
+export function WithTags(Base) {
+    return class extends Base {
+        static getTags() { }
+        tags() { }
+    };
+}
+export class Test extends WithTags(FooItem) {
+}
+export class Test2 {
+    nested = class {
+        #prop = 42;
+    };
+}
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile3.symbols b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.symbols
new file mode 100644
index 0000000000000..dbb2854de4360
--- /dev/null
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.symbols
@@ -0,0 +1,73 @@
+//// [tests/cases/compiler/emitClassExpressionInDeclarationFile3.ts] ////
+
+=== emitClassExpressionInDeclarationFile3.ts ===
+export var noPrivates = class {
+>noPrivates : Symbol(noPrivates, Decl(emitClassExpressionInDeclarationFile3.ts, 0, 10))
+
+    static getTags() { }
+>getTags : Symbol(noPrivates.getTags, Decl(emitClassExpressionInDeclarationFile3.ts, 0, 31))
+
+    tags() { }
+>tags : Symbol(noPrivates.tags, Decl(emitClassExpressionInDeclarationFile3.ts, 1, 24))
+
+    static #ps = -1
+>#ps : Symbol(noPrivates.#ps, Decl(emitClassExpressionInDeclarationFile3.ts, 2, 14))
+
+    #p = 12
+>#p : Symbol(noPrivates.#p, Decl(emitClassExpressionInDeclarationFile3.ts, 3, 19))
+}
+
+export class FooItem {
+>FooItem : Symbol(FooItem, Decl(emitClassExpressionInDeclarationFile3.ts, 5, 1))
+
+    foo(): void { }
+>foo : Symbol(FooItem.foo, Decl(emitClassExpressionInDeclarationFile3.ts, 7, 22))
+
+    name?: string;
+>name : Symbol(FooItem.name, Decl(emitClassExpressionInDeclarationFile3.ts, 8, 19))
+
+    #property = "capitalism"
+>#property : Symbol(FooItem.#property, Decl(emitClassExpressionInDeclarationFile3.ts, 9, 18))
+}
+
+export type Constructor<T> = new(...args: any[]) => T;
+>Constructor : Symbol(Constructor, Decl(emitClassExpressionInDeclarationFile3.ts, 11, 1))
+>T : Symbol(T, Decl(emitClassExpressionInDeclarationFile3.ts, 13, 24))
+>args : Symbol(args, Decl(emitClassExpressionInDeclarationFile3.ts, 13, 33))
+>T : Symbol(T, Decl(emitClassExpressionInDeclarationFile3.ts, 13, 24))
+
+export function WithTags<T extends Constructor<FooItem>>(Base: T) {
+>WithTags : Symbol(WithTags, Decl(emitClassExpressionInDeclarationFile3.ts, 13, 54))
+>T : Symbol(T, Decl(emitClassExpressionInDeclarationFile3.ts, 14, 25))
+>Constructor : Symbol(Constructor, Decl(emitClassExpressionInDeclarationFile3.ts, 11, 1))
+>FooItem : Symbol(FooItem, Decl(emitClassExpressionInDeclarationFile3.ts, 5, 1))
+>Base : Symbol(Base, Decl(emitClassExpressionInDeclarationFile3.ts, 14, 57))
+>T : Symbol(T, Decl(emitClassExpressionInDeclarationFile3.ts, 14, 25))
+
+    return class extends Base {
+>Base : Symbol(Base, Decl(emitClassExpressionInDeclarationFile3.ts, 14, 57))
+
+        static getTags(): void { }
+>getTags : Symbol((Anonymous class).getTags, Decl(emitClassExpressionInDeclarationFile3.ts, 15, 31))
+
+        tags(): void { }
+>tags : Symbol((Anonymous class).tags, Decl(emitClassExpressionInDeclarationFile3.ts, 16, 34))
+    }
+}
+
+export class Test extends WithTags(FooItem) {}
+>Test : Symbol(Test, Decl(emitClassExpressionInDeclarationFile3.ts, 19, 1))
+>WithTags : Symbol(WithTags, Decl(emitClassExpressionInDeclarationFile3.ts, 13, 54))
+>FooItem : Symbol(FooItem, Decl(emitClassExpressionInDeclarationFile3.ts, 5, 1))
+
+export class Test2 {
+>Test2 : Symbol(Test2, Decl(emitClassExpressionInDeclarationFile3.ts, 21, 46))
+
+  nested = class {
+>nested : Symbol(Test2.nested, Decl(emitClassExpressionInDeclarationFile3.ts, 23, 20))
+
+    #prop = 42;
+>#prop : Symbol((Anonymous class).#prop, Decl(emitClassExpressionInDeclarationFile3.ts, 24, 18))
+  }
+}
+
diff --git a/tests/baselines/reference/emitClassExpressionInDeclarationFile3.types b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.types
new file mode 100644
index 0000000000000..d72a88b2f0a2a
--- /dev/null
+++ b/tests/baselines/reference/emitClassExpressionInDeclarationFile3.types
@@ -0,0 +1,107 @@
+//// [tests/cases/compiler/emitClassExpressionInDeclarationFile3.ts] ////
+
+=== emitClassExpressionInDeclarationFile3.ts ===
+export var noPrivates = class {
+>noPrivates : typeof noPrivates
+>           : ^^^^^^^^^^^^^^^^^
+>class {    static getTags() { }    tags() { }    static #ps = -1    #p = 12} : typeof noPrivates
+>                                                                             : ^^^^^^^^^^^^^^^^^
+
+    static getTags() { }
+>getTags : () => void
+>        : ^^^^^^^^^^
+
+    tags() { }
+>tags : () => void
+>     : ^^^^^^^^^^
+
+    static #ps = -1
+>#ps : number
+>    : ^^^^^^
+>-1 : -1
+>   : ^^
+>1 : 1
+>  : ^
+
+    #p = 12
+>#p : number
+>   : ^^^^^^
+>12 : 12
+>   : ^^
+}
+
+export class FooItem {
+>FooItem : FooItem
+>        : ^^^^^^^
+
+    foo(): void { }
+>foo : () => void
+>    : ^^^^^^    
+
+    name?: string;
+>name : string
+>     : ^^^^^^
+
+    #property = "capitalism"
+>#property : string
+>          : ^^^^^^
+>"capitalism" : "capitalism"
+>             : ^^^^^^^^^^^^
+}
+
+export type Constructor<T> = new(...args: any[]) => T;
+>Constructor : Constructor<T>
+>            : ^^^^^^^^^^^^^^
+>args : any[]
+>     : ^^^^^
+
+export function WithTags<T extends Constructor<FooItem>>(Base: T) {
+>WithTags : <T extends Constructor<FooItem>>(Base: T) => { new (...args: any[]): (Anonymous class); prototype: WithTags<any>.(Anonymous class); getTags(): void; } & T
+>         : ^ ^^^^^^^^^                    ^^    ^^ ^^^^^^^^^^^^^^^    ^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^    ^^^^^^^
+>Base : T
+>     : ^
+
+    return class extends Base {
+>class extends Base {        static getTags(): void { }        tags(): void { }    } : { new (...args: any[]): (Anonymous class); prototype: WithTags<any>.(Anonymous class); getTags(): void; } & T
+>                                                                                    : ^^^^^^^^^^    ^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^    ^^^^^^^
+>Base : FooItem
+>     : ^^^^^^^
+
+        static getTags(): void { }
+>getTags : () => void
+>        : ^^^^^^    
+
+        tags(): void { }
+>tags : () => void
+>     : ^^^^^^    
+    }
+}
+
+export class Test extends WithTags(FooItem) {}
+>Test : Test
+>     : ^^^^
+>WithTags(FooItem) : WithTags<typeof FooItem>.(Anonymous class) & FooItem
+>                  : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>WithTags : <T extends Constructor<FooItem>>(Base: T) => { new (...args: any[]): (Anonymous class); prototype: WithTags<any>.(Anonymous class); getTags(): void; } & T
+>         : ^ ^^^^^^^^^                    ^^    ^^ ^^^^^^^^^^^^^^^    ^^     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^    ^^^^^^^
+>FooItem : typeof FooItem
+>        : ^^^^^^^^^^^^^^
+
+export class Test2 {
+>Test2 : Test2
+>      : ^^^^^
+
+  nested = class {
+>nested : typeof (Anonymous class)
+>       : ^^^^^^^^^^^^^^^^^^^^^^^^
+>class {    #prop = 42;  } : typeof (Anonymous class)
+>                          : ^^^^^^^^^^^^^^^^^^^^^^^^
+
+    #prop = 42;
+>#prop : number
+>      : ^^^^^^
+>42 : 42
+>   : ^^
+  }
+}
+
diff --git a/tests/cases/compiler/declarationEmitMixinPrivateField1.ts b/tests/cases/compiler/declarationEmitMixinPrivateField1.ts
new file mode 100644
index 0000000000000..93a062f8ce8a7
--- /dev/null
+++ b/tests/cases/compiler/declarationEmitMixinPrivateField1.ts
@@ -0,0 +1,20 @@
+// @target: esnext
+// @declaration: true
+// @filename: first.ts
+declare function mix<TMix>(mixin: TMix): TMix;
+
+const DisposableMixin = class {
+    #onDispose() {}
+};
+
+export default mix(DisposableMixin);
+export class Monitor extends mix(DisposableMixin) {}
+
+// @filename: another.ts
+declare function mix<TMix>(mixin: TMix): TMix;
+
+const DisposableMixin = class {
+    #onDispose() {}
+};
+
+export default class extends mix(DisposableMixin) {}
diff --git a/tests/cases/compiler/emitClassExpressionInDeclarationFile2.ts b/tests/cases/compiler/emitClassExpressionInDeclarationFile2.ts
index 3175f2afce7df..853986f4a2e19 100644
--- a/tests/cases/compiler/emitClassExpressionInDeclarationFile2.ts
+++ b/tests/cases/compiler/emitClassExpressionInDeclarationFile2.ts
@@ -27,3 +27,9 @@ const test = new Test();
 
 Test.getTags()
 test.tags();
+
+export class Test2 {
+  nested = class {
+    private prop = 42;
+  }
+}
diff --git a/tests/cases/compiler/emitClassExpressionInDeclarationFile3.ts b/tests/cases/compiler/emitClassExpressionInDeclarationFile3.ts
new file mode 100644
index 0000000000000..205e782cddad1
--- /dev/null
+++ b/tests/cases/compiler/emitClassExpressionInDeclarationFile3.ts
@@ -0,0 +1,31 @@
+// @target: esnext
+// @declaration: true
+
+export var noPrivates = class {
+    static getTags() { }
+    tags() { }
+    static #ps = -1
+    #p = 12
+}
+
+export class FooItem {
+    foo(): void { }
+    name?: string;
+    #property = "capitalism"
+}
+
+export type Constructor<T> = new(...args: any[]) => T;
+export function WithTags<T extends Constructor<FooItem>>(Base: T) {
+    return class extends Base {
+        static getTags(): void { }
+        tags(): void { }
+    }
+}
+
+export class Test extends WithTags(FooItem) {}
+
+export class Test2 {
+  nested = class {
+    #prop = 42;
+  }
+}