diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 27d0617c5affa..3965665ba19e1 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -12623,7 +12623,7 @@ namespace ts {
           * callable `then` signature.
           */
         function checkAsyncFunctionReturnType(node: FunctionLikeDeclaration): Type {
-            if (languageVersion >= ScriptTarget.ES6) {
+            if (compilerOptions.noCustomAsyncPromise && languageVersion >= ScriptTarget.ES6) {
                 const returnType = getTypeFromTypeNode(node.type);
                 return checkCorrectPromiseType(returnType, node.type);
             }
@@ -13029,6 +13029,10 @@ namespace ts {
         }
 
         function checkCollisionWithGlobalPromiseInGeneratedCode(node: Node, name: Identifier): void {
+            if (!compilerOptions.noCustomAsyncPromise) {
+                return;
+            }
+
             if (!needCollisionCheckForIdentifier(node, name, "Promise")) {
                 return;
             }
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 5bbd74d6f47f4..0a4481483c577 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -299,6 +299,11 @@ namespace ts {
             name: "noImplicitUseStrict",
             type: "boolean",
             description: Diagnostics.Do_not_emit_use_strict_directives_in_module_output
+        },
+        {
+            name: "noCustomAsyncPromise",
+            type: "boolean",
+            experimental: true
         }
     ];
 
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 72614756fb79c..212d9f05510d9 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -296,11 +296,11 @@ namespace ts {
      * If loop contains block scoped binding captured in some function then loop body is converted to a function.
      * Lexical bindings declared in loop initializer will be passed into the loop body function as parameters,
      * however if this binding is modified inside the body - this new value should be propagated back to the original binding.
-     * This is done by declaring new variable (out parameter holder) outside of the loop for every binding that is reassigned inside the body. 
+     * This is done by declaring new variable (out parameter holder) outside of the loop for every binding that is reassigned inside the body.
      * On every iteration this variable is initialized with value of corresponding binding.
      * At every point where control flow leaves the loop either explicitly (break/continue) or implicitly (at the end of loop body)
      * we copy the value inside the loop to the out parameter holder.
-     * 
+     *
      * for (let x;;) {
      *     let a = 1;
      *     let b = () => a;
@@ -308,9 +308,9 @@ namespace ts {
      *     if (...) break;
      *     ...
      * }
-     * 
+     *
      * will be converted to
-     * 
+     *
      * var out_x;
      * var loop = function(x) {
      *     var a = 1;
@@ -326,7 +326,7 @@ namespace ts {
      *     x = out_x;
      *     if (state === "break") break;
      * }
-     * 
+     *
      * NOTE: values to out parameters are not copies if loop is abrupted with 'return' - in this case this will end the entire enclosing function
      * so nobody can observe this new value.
      */
@@ -3049,7 +3049,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
                 }
 
                 writeLine();
-                // end of loop body -> copy out parameter 
+                // end of loop body -> copy out parameter
                 copyLoopOutParameters(convertedLoopState, CopyDirection.ToOutParameter, /*emitAsStatements*/true);
 
                 decreaseIndent();
@@ -4685,7 +4685,7 @@ const _super = (function (geti, seti) {
                     write(", void 0, ");
                 }
 
-                if (languageVersion >= ScriptTarget.ES6 || !promiseConstructor) {
+                if (!promiseConstructor || (compilerOptions.noCustomAsyncPromise && languageVersion >= ScriptTarget.ES6)) {
                     write("void 0");
                 }
                 else {
@@ -7245,7 +7245,7 @@ const _super = (function (geti, seti) {
                     }
 
                     // text should be quoted string
-                    // for deduplication purposes in key remove leading and trailing quotes so 'a' and "a" will be considered the same                     
+                    // for deduplication purposes in key remove leading and trailing quotes so 'a' and "a" will be considered the same
                     const key = text.substr(1, text.length - 2);
 
                     if (hasProperty(groupIndices, key)) {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 31ff055f986a2..d57ec88892bb7 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2442,6 +2442,8 @@ namespace ts {
         /* @internal */ skipDefaultLibCheck?: boolean;
         // Do not perform validation of output file name in transpile scenarios
         /* @internal */ suppressOutputPathCheck?: boolean;
+        // Disallow custom promise return types in async functions.
+        /* @internal */ noCustomAsyncPromise?: boolean;
 
         [option: string]: string | number | boolean;
     }
diff --git a/tests/baselines/reference/asyncAliasReturnType_es6.errors.txt b/tests/baselines/reference/asyncAliasReturnType_es6.errors.txt
new file mode 100644
index 0000000000000..ec532d1380d20
--- /dev/null
+++ b/tests/baselines/reference/asyncAliasReturnType_es6.errors.txt
@@ -0,0 +1,10 @@
+tests/cases/conformance/async/es6/asyncAliasReturnType_es6.ts(3,16): error TS1055: Type 'PromiseAlias' is not a valid async function return type.
+
+
+==== tests/cases/conformance/async/es6/asyncAliasReturnType_es6.ts (1 errors) ====
+    type PromiseAlias<T> = Promise<T>;
+    
+    async function f(): PromiseAlias<void> {
+                   ~
+!!! error TS1055: Type 'PromiseAlias' is not a valid async function return type.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncAliasReturnType_es6.js b/tests/baselines/reference/asyncAliasReturnType_es6.js
index 45fe3228f6ebd..0af63b0bfa604 100644
--- a/tests/baselines/reference/asyncAliasReturnType_es6.js
+++ b/tests/baselines/reference/asyncAliasReturnType_es6.js
@@ -6,6 +6,6 @@ async function f(): PromiseAlias<void> {
 
 //// [asyncAliasReturnType_es6.js]
 function f() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, PromiseAlias, function* () {
     });
 }
diff --git a/tests/baselines/reference/asyncAliasReturnType_es6.symbols b/tests/baselines/reference/asyncAliasReturnType_es6.symbols
deleted file mode 100644
index 4d6db6a1ef4c4..0000000000000
--- a/tests/baselines/reference/asyncAliasReturnType_es6.symbols
+++ /dev/null
@@ -1,11 +0,0 @@
-=== tests/cases/conformance/async/es6/asyncAliasReturnType_es6.ts ===
-type PromiseAlias<T> = Promise<T>;
->PromiseAlias : Symbol(PromiseAlias, Decl(asyncAliasReturnType_es6.ts, 0, 0))
->T : Symbol(T, Decl(asyncAliasReturnType_es6.ts, 0, 18))
->Promise : Symbol(Promise, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
->T : Symbol(T, Decl(asyncAliasReturnType_es6.ts, 0, 18))
-
-async function f(): PromiseAlias<void> {
->f : Symbol(f, Decl(asyncAliasReturnType_es6.ts, 0, 34))
->PromiseAlias : Symbol(PromiseAlias, Decl(asyncAliasReturnType_es6.ts, 0, 0))
-}
diff --git a/tests/baselines/reference/asyncAliasReturnType_es6.types b/tests/baselines/reference/asyncAliasReturnType_es6.types
deleted file mode 100644
index 8426d2a3542f4..0000000000000
--- a/tests/baselines/reference/asyncAliasReturnType_es6.types
+++ /dev/null
@@ -1,11 +0,0 @@
-=== tests/cases/conformance/async/es6/asyncAliasReturnType_es6.ts ===
-type PromiseAlias<T> = Promise<T>;
->PromiseAlias : Promise<T>
->T : T
->Promise : Promise<T>
->T : T
-
-async function f(): PromiseAlias<void> {
->f : () => Promise<void>
->PromiseAlias : Promise<T>
-}
diff --git a/tests/baselines/reference/asyncArrowFunction1_es6.js b/tests/baselines/reference/asyncArrowFunction1_es6.js
index 0026cd91a7ef9..4f03acc5ced43 100644
--- a/tests/baselines/reference/asyncArrowFunction1_es6.js
+++ b/tests/baselines/reference/asyncArrowFunction1_es6.js
@@ -4,5 +4,5 @@ var foo = async (): Promise<void> => {
 };
 
 //// [asyncArrowFunction1_es6.js]
-var foo = () => __awaiter(this, void 0, void 0, function* () {
+var foo = () => __awaiter(this, void 0, Promise, function* () {
 });
diff --git a/tests/baselines/reference/asyncArrowFunction6_es6.js b/tests/baselines/reference/asyncArrowFunction6_es6.js
index a01e53f5b114f..54b8aa1f6b154 100644
--- a/tests/baselines/reference/asyncArrowFunction6_es6.js
+++ b/tests/baselines/reference/asyncArrowFunction6_es6.js
@@ -4,5 +4,5 @@ var foo = async (a = await): Promise<void> => {
 }
 
 //// [asyncArrowFunction6_es6.js]
-var foo = (a = yield ) => __awaiter(this, void 0, void 0, function* () {
+var foo = (a = yield ) => __awaiter(this, void 0, Promise, function* () {
 });
diff --git a/tests/baselines/reference/asyncArrowFunction7_es6.js b/tests/baselines/reference/asyncArrowFunction7_es6.js
index fab705c0b76e2..ac68a8fd2f865 100644
--- a/tests/baselines/reference/asyncArrowFunction7_es6.js
+++ b/tests/baselines/reference/asyncArrowFunction7_es6.js
@@ -7,8 +7,8 @@ var bar = async (): Promise<void> => {
 }
 
 //// [asyncArrowFunction7_es6.js]
-var bar = () => __awaiter(this, void 0, void 0, function* () {
+var bar = () => __awaiter(this, void 0, Promise, function* () {
     // 'await' here is an identifier, and not an await expression.
-    var foo = (a = yield ) => __awaiter(this, void 0, void 0, function* () {
+    var foo = (a = yield ) => __awaiter(this, void 0, Promise, function* () {
     });
 });
diff --git a/tests/baselines/reference/asyncArrowFunction8_es6.js b/tests/baselines/reference/asyncArrowFunction8_es6.js
index 0c33cfcfa2de0..9cee5ee1525d7 100644
--- a/tests/baselines/reference/asyncArrowFunction8_es6.js
+++ b/tests/baselines/reference/asyncArrowFunction8_es6.js
@@ -5,6 +5,6 @@ var foo = async (): Promise<void> => {
 }
 
 //// [asyncArrowFunction8_es6.js]
-var foo = () => __awaiter(this, void 0, void 0, function* () {
+var foo = () => __awaiter(this, void 0, Promise, function* () {
     var v = { [yield ]: foo };
 });
diff --git a/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js b/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js
index 4022fde7f54e8..2feb26d6fafd5 100644
--- a/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js
+++ b/tests/baselines/reference/asyncAwaitIsolatedModules_es6.js
@@ -52,36 +52,36 @@ function f0() {
     return __awaiter(this, void 0, void 0, function* () { });
 }
 function f1() {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, Promise, function* () { });
 }
 function f3() {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, MyPromise, function* () { });
 }
 let f4 = function () {
     return __awaiter(this, void 0, void 0, function* () { });
 };
 let f5 = function () {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, Promise, function* () { });
 };
 let f6 = function () {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, MyPromise, function* () { });
 };
 let f7 = () => __awaiter(this, void 0, void 0, function* () { });
-let f8 = () => __awaiter(this, void 0, void 0, function* () { });
-let f9 = () => __awaiter(this, void 0, void 0, function* () { });
+let f8 = () => __awaiter(this, void 0, Promise, function* () { });
+let f9 = () => __awaiter(this, void 0, MyPromise, function* () { });
 let f10 = () => __awaiter(this, void 0, void 0, function* () { return p; });
 let f11 = () => __awaiter(this, void 0, void 0, function* () { return mp; });
-let f12 = () => __awaiter(this, void 0, void 0, function* () { return mp; });
-let f13 = () => __awaiter(this, void 0, void 0, function* () { return p; });
+let f12 = () => __awaiter(this, void 0, Promise, function* () { return mp; });
+let f13 = () => __awaiter(this, void 0, MyPromise, function* () { return p; });
 let o = {
     m1() {
         return __awaiter(this, void 0, void 0, function* () { });
     },
     m2() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, Promise, function* () { });
     },
     m3() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, MyPromise, function* () { });
     }
 };
 class C {
@@ -89,19 +89,19 @@ class C {
         return __awaiter(this, void 0, void 0, function* () { });
     }
     m2() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, Promise, function* () { });
     }
     m3() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, MyPromise, function* () { });
     }
     static m4() {
         return __awaiter(this, void 0, void 0, function* () { });
     }
     static m5() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, Promise, function* () { });
     }
     static m6() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, MyPromise, function* () { });
     }
 }
 var M;
diff --git a/tests/baselines/reference/asyncAwait_es6.js b/tests/baselines/reference/asyncAwait_es6.js
index be2eb90e3e4fb..f15a8e2df7c0a 100644
--- a/tests/baselines/reference/asyncAwait_es6.js
+++ b/tests/baselines/reference/asyncAwait_es6.js
@@ -52,36 +52,36 @@ function f0() {
     return __awaiter(this, void 0, void 0, function* () { });
 }
 function f1() {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, Promise, function* () { });
 }
 function f3() {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, MyPromise, function* () { });
 }
 let f4 = function () {
     return __awaiter(this, void 0, void 0, function* () { });
 };
 let f5 = function () {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, Promise, function* () { });
 };
 let f6 = function () {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, MyPromise, function* () { });
 };
 let f7 = () => __awaiter(this, void 0, void 0, function* () { });
-let f8 = () => __awaiter(this, void 0, void 0, function* () { });
-let f9 = () => __awaiter(this, void 0, void 0, function* () { });
+let f8 = () => __awaiter(this, void 0, Promise, function* () { });
+let f9 = () => __awaiter(this, void 0, MyPromise, function* () { });
 let f10 = () => __awaiter(this, void 0, void 0, function* () { return p; });
 let f11 = () => __awaiter(this, void 0, void 0, function* () { return mp; });
-let f12 = () => __awaiter(this, void 0, void 0, function* () { return mp; });
-let f13 = () => __awaiter(this, void 0, void 0, function* () { return p; });
+let f12 = () => __awaiter(this, void 0, Promise, function* () { return mp; });
+let f13 = () => __awaiter(this, void 0, MyPromise, function* () { return p; });
 let o = {
     m1() {
         return __awaiter(this, void 0, void 0, function* () { });
     },
     m2() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, Promise, function* () { });
     },
     m3() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, MyPromise, function* () { });
     }
 };
 class C {
@@ -89,19 +89,19 @@ class C {
         return __awaiter(this, void 0, void 0, function* () { });
     }
     m2() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, Promise, function* () { });
     }
     m3() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, MyPromise, function* () { });
     }
     static m4() {
         return __awaiter(this, void 0, void 0, function* () { });
     }
     static m5() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, Promise, function* () { });
     }
     static m6() {
-        return __awaiter(this, void 0, void 0, function* () { });
+        return __awaiter(this, void 0, MyPromise, function* () { });
     }
 }
 var M;
diff --git a/tests/baselines/reference/asyncFunctionDeclaration11_es6.js b/tests/baselines/reference/asyncFunctionDeclaration11_es6.js
index 6fe8921434c84..a44343cef7822 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration11_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration11_es6.js
@@ -4,6 +4,6 @@ async function await(): Promise<void> {
 
 //// [asyncFunctionDeclaration11_es6.js]
 function await() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
     });
 }
diff --git a/tests/baselines/reference/asyncFunctionDeclaration13_es6.js b/tests/baselines/reference/asyncFunctionDeclaration13_es6.js
index 6fab6c39947d3..4257c8691c25b 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration13_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration13_es6.js
@@ -7,7 +7,7 @@ async function foo(): Promise<void> {
 
 //// [asyncFunctionDeclaration13_es6.js]
 function foo() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         // Legal to use 'await' in a type context.
         var v;
     });
diff --git a/tests/baselines/reference/asyncFunctionDeclaration14_es6.js b/tests/baselines/reference/asyncFunctionDeclaration14_es6.js
index f584f9178426f..f32d106f92e37 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration14_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration14_es6.js
@@ -5,7 +5,7 @@ async function foo(): Promise<void> {
 
 //// [asyncFunctionDeclaration14_es6.js]
 function foo() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         return;
     });
 }
diff --git a/tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt b/tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt
index e8d3e7d79b1e8..29158d9053bf8 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt
+++ b/tests/baselines/reference/asyncFunctionDeclaration15_es6.errors.txt
@@ -1,33 +1,44 @@
-tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(6,23): error TS1064: The return type of an async function or method must be the global Promise<T> type.
-tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(7,23): error TS1064: The return type of an async function or method must be the global Promise<T> type.
-tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(8,23): error TS1064: The return type of an async function or method must be the global Promise<T> type.
-tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(9,23): error TS1064: The return type of an async function or method must be the global Promise<T> type.
-tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(10,23): error TS1064: The return type of an async function or method must be the global Promise<T> type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(6,16): error TS1055: Type '{}' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(7,16): error TS1055: Type 'any' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(8,16): error TS1055: Type 'number' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(9,16): error TS1055: Type 'PromiseLike' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(10,16): error TS1055: Type 'typeof Thenable' is not a valid async function return type.
+tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(10,16): error TS1055: Type 'typeof Thenable' is not a valid async function return type.
+  Type 'Thenable' is not assignable to type 'PromiseLike<any>'.
+    Types of property 'then' are incompatible.
+      Type '() => void' is not assignable to type '{ <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => TResult | PromiseLike<TResult>): PromiseLike<TResult>; <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => void): PromiseLike<TResult>; }'.
+        Type 'void' is not assignable to type 'PromiseLike<any>'.
 tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(17,16): error TS1059: Return expression in async function does not have a valid callable 'then' member.
 tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts(23,25): error TS1058: Operand for 'await' does not have a valid callable 'then' member.
 
 
-==== tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts (7 errors) ====
+==== tests/cases/conformance/async/es6/functionDeclarations/asyncFunctionDeclaration15_es6.ts (8 errors) ====
     declare class Thenable { then(): void; }
     declare let a: any;
     declare let obj: { then: string; };
     declare let thenable: Thenable;
     async function fn1() { } // valid: Promise<void>
     async function fn2(): { } { } // error
-                          ~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
+                   ~~~
+!!! error TS1055: Type '{}' is not a valid async function return type.
     async function fn3(): any { } // error
-                          ~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
+                   ~~~
+!!! error TS1055: Type 'any' is not a valid async function return type.
     async function fn4(): number { } // error
-                          ~~~~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
+                   ~~~
+!!! error TS1055: Type 'number' is not a valid async function return type.
     async function fn5(): PromiseLike<void> { } // error
-                          ~~~~~~~~~~~~~~~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
+                   ~~~
+!!! error TS1055: Type 'PromiseLike' is not a valid async function return type.
     async function fn6(): Thenable { } // error
-                          ~~~~~~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
+                   ~~~
+!!! error TS1055: Type 'typeof Thenable' is not a valid async function return type.
+                   ~~~
+!!! error TS1055: Type 'typeof Thenable' is not a valid async function return type.
+!!! error TS1055:   Type 'Thenable' is not assignable to type 'PromiseLike<any>'.
+!!! error TS1055:     Types of property 'then' are incompatible.
+!!! error TS1055:       Type '() => void' is not assignable to type '{ <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => TResult | PromiseLike<TResult>): PromiseLike<TResult>; <TResult>(onfulfilled?: (value: any) => TResult | PromiseLike<TResult>, onrejected?: (reason: any) => void): PromiseLike<TResult>; }'.
+!!! error TS1055:         Type 'void' is not assignable to type 'PromiseLike<any>'.
     async function fn7() { return; } // valid: Promise<void>
     async function fn8() { return 1; } // valid: Promise<number>
     async function fn9() { return null; } // valid: Promise<any>
diff --git a/tests/baselines/reference/asyncFunctionDeclaration15_es6.js b/tests/baselines/reference/asyncFunctionDeclaration15_es6.js
index 174a95d6f669f..0efbd6f66f98a 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration15_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration15_es6.js
@@ -38,10 +38,10 @@ function fn4() {
     return __awaiter(this, void 0, void 0, function* () { });
 } // error
 function fn5() {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, PromiseLike, function* () { });
 } // error
 function fn6() {
-    return __awaiter(this, void 0, void 0, function* () { });
+    return __awaiter(this, void 0, Thenable, function* () { });
 } // error
 function fn7() {
     return __awaiter(this, void 0, void 0, function* () { return; });
diff --git a/tests/baselines/reference/asyncFunctionDeclaration1_es6.js b/tests/baselines/reference/asyncFunctionDeclaration1_es6.js
index e92d55dc0e2ce..263e27fa35efa 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration1_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration1_es6.js
@@ -4,6 +4,6 @@ async function foo(): Promise<void> {
 
 //// [asyncFunctionDeclaration1_es6.js]
 function foo() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
     });
 }
diff --git a/tests/baselines/reference/asyncFunctionDeclaration6_es6.js b/tests/baselines/reference/asyncFunctionDeclaration6_es6.js
index a70316989b380..8c37968ab4c22 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration6_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration6_es6.js
@@ -4,6 +4,6 @@ async function foo(a = await): Promise<void> {
 
 //// [asyncFunctionDeclaration6_es6.js]
 function foo(a = yield ) {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
     });
 }
diff --git a/tests/baselines/reference/asyncFunctionDeclaration7_es6.js b/tests/baselines/reference/asyncFunctionDeclaration7_es6.js
index 0d360fa866ccb..ef66df4e4133a 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration7_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration7_es6.js
@@ -7,10 +7,10 @@ async function bar(): Promise<void> {
 
 //// [asyncFunctionDeclaration7_es6.js]
 function bar() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         // 'await' here is an identifier, and not a yield expression.
         function foo(a = yield ) {
-            return __awaiter(this, void 0, void 0, function* () {
+            return __awaiter(this, void 0, Promise, function* () {
             });
         }
     });
diff --git a/tests/baselines/reference/asyncFunctionDeclaration9_es6.js b/tests/baselines/reference/asyncFunctionDeclaration9_es6.js
index c57c0eb395a72..9723a69f2a23b 100644
--- a/tests/baselines/reference/asyncFunctionDeclaration9_es6.js
+++ b/tests/baselines/reference/asyncFunctionDeclaration9_es6.js
@@ -5,7 +5,7 @@ async function foo(): Promise<void> {
 
 //// [asyncFunctionDeclaration9_es6.js]
 function foo() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         var v = { [yield ]: foo };
     });
 }
diff --git a/tests/baselines/reference/asyncImportedPromise_es6.errors.txt b/tests/baselines/reference/asyncImportedPromise_es6.errors.txt
deleted file mode 100644
index 43b454826447c..0000000000000
--- a/tests/baselines/reference/asyncImportedPromise_es6.errors.txt
+++ /dev/null
@@ -1,13 +0,0 @@
-tests/cases/conformance/async/es6/test.ts(3,25): error TS1064: The return type of an async function or method must be the global Promise<T> type.
-
-
-==== tests/cases/conformance/async/es6/task.ts (0 errors) ====
-    export class Task<T> extends Promise<T> { }
-    
-==== tests/cases/conformance/async/es6/test.ts (1 errors) ====
-    import { Task } from "./task";
-    class Test {
-        async example<T>(): Task<T> { return; }
-                            ~~~~~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncImportedPromise_es6.js b/tests/baselines/reference/asyncImportedPromise_es6.js
index 56a41b0283f5b..8cad65e6d5b0b 100644
--- a/tests/baselines/reference/asyncImportedPromise_es6.js
+++ b/tests/baselines/reference/asyncImportedPromise_es6.js
@@ -24,8 +24,9 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
         step((generator = generator.apply(thisArg, _arguments)).next());
     });
 };
+const task_1 = require("./task");
 class Test {
     example() {
-        return __awaiter(this, void 0, void 0, function* () { return; });
+        return __awaiter(this, void 0, task_1.Task, function* () { return; });
     }
 }
diff --git a/tests/baselines/reference/asyncImportedPromise_es6.symbols b/tests/baselines/reference/asyncImportedPromise_es6.symbols
new file mode 100644
index 0000000000000..45cf47d2b45b2
--- /dev/null
+++ b/tests/baselines/reference/asyncImportedPromise_es6.symbols
@@ -0,0 +1,20 @@
+=== tests/cases/conformance/async/es6/task.ts ===
+export class Task<T> extends Promise<T> { }
+>Task : Symbol(Task, Decl(task.ts, 0, 0))
+>T : Symbol(T, Decl(task.ts, 0, 18))
+>Promise : Symbol(Promise, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>T : Symbol(T, Decl(task.ts, 0, 18))
+
+=== tests/cases/conformance/async/es6/test.ts ===
+import { Task } from "./task";
+>Task : Symbol(Task, Decl(test.ts, 0, 8))
+
+class Test {
+>Test : Symbol(Test, Decl(test.ts, 0, 30))
+
+    async example<T>(): Task<T> { return; }
+>example : Symbol(example, Decl(test.ts, 1, 12))
+>T : Symbol(T, Decl(test.ts, 2, 18))
+>Task : Symbol(Task, Decl(test.ts, 0, 8))
+>T : Symbol(T, Decl(test.ts, 2, 18))
+}
diff --git a/tests/baselines/reference/asyncImportedPromise_es6.types b/tests/baselines/reference/asyncImportedPromise_es6.types
new file mode 100644
index 0000000000000..424f14b34d37f
--- /dev/null
+++ b/tests/baselines/reference/asyncImportedPromise_es6.types
@@ -0,0 +1,20 @@
+=== tests/cases/conformance/async/es6/task.ts ===
+export class Task<T> extends Promise<T> { }
+>Task : Task<T>
+>T : T
+>Promise : Promise<T>
+>T : T
+
+=== tests/cases/conformance/async/es6/test.ts ===
+import { Task } from "./task";
+>Task : typeof Task
+
+class Test {
+>Test : Test
+
+    async example<T>(): Task<T> { return; }
+>example : <T>() => Task<T>
+>T : T
+>Task : Task<T>
+>T : T
+}
diff --git a/tests/baselines/reference/asyncQualifiedReturnType_es6.errors.txt b/tests/baselines/reference/asyncQualifiedReturnType_es6.errors.txt
deleted file mode 100644
index 205ea01673631..0000000000000
--- a/tests/baselines/reference/asyncQualifiedReturnType_es6.errors.txt
+++ /dev/null
@@ -1,13 +0,0 @@
-tests/cases/conformance/async/es6/asyncQualifiedReturnType_es6.ts(6,21): error TS1064: The return type of an async function or method must be the global Promise<T> type.
-
-
-==== tests/cases/conformance/async/es6/asyncQualifiedReturnType_es6.ts (1 errors) ====
-    namespace X {
-        export class MyPromise<T> extends Promise<T> {
-        }
-    }
-    
-    async function f(): X.MyPromise<void> {
-                        ~~~~~~~~~~~~~~~~~
-!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/asyncQualifiedReturnType_es6.js b/tests/baselines/reference/asyncQualifiedReturnType_es6.js
index 4d5aa87bbffb4..1da37946254f6 100644
--- a/tests/baselines/reference/asyncQualifiedReturnType_es6.js
+++ b/tests/baselines/reference/asyncQualifiedReturnType_es6.js
@@ -15,6 +15,6 @@ var X;
     X.MyPromise = MyPromise;
 })(X || (X = {}));
 function f() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, X.MyPromise, function* () {
     });
 }
diff --git a/tests/baselines/reference/asyncQualifiedReturnType_es6.symbols b/tests/baselines/reference/asyncQualifiedReturnType_es6.symbols
new file mode 100644
index 0000000000000..5d27d04ea3bdc
--- /dev/null
+++ b/tests/baselines/reference/asyncQualifiedReturnType_es6.symbols
@@ -0,0 +1,17 @@
+=== tests/cases/conformance/async/es6/asyncQualifiedReturnType_es6.ts ===
+namespace X {
+>X : Symbol(X, Decl(asyncQualifiedReturnType_es6.ts, 0, 0))
+
+    export class MyPromise<T> extends Promise<T> {
+>MyPromise : Symbol(MyPromise, Decl(asyncQualifiedReturnType_es6.ts, 0, 13))
+>T : Symbol(T, Decl(asyncQualifiedReturnType_es6.ts, 1, 27))
+>Promise : Symbol(Promise, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>T : Symbol(T, Decl(asyncQualifiedReturnType_es6.ts, 1, 27))
+    }
+}
+
+async function f(): X.MyPromise<void> {
+>f : Symbol(f, Decl(asyncQualifiedReturnType_es6.ts, 3, 1))
+>X : Symbol(X, Decl(asyncQualifiedReturnType_es6.ts, 0, 0))
+>MyPromise : Symbol(X.MyPromise, Decl(asyncQualifiedReturnType_es6.ts, 0, 13))
+}
diff --git a/tests/baselines/reference/asyncQualifiedReturnType_es6.types b/tests/baselines/reference/asyncQualifiedReturnType_es6.types
new file mode 100644
index 0000000000000..3b438eb93b68a
--- /dev/null
+++ b/tests/baselines/reference/asyncQualifiedReturnType_es6.types
@@ -0,0 +1,17 @@
+=== tests/cases/conformance/async/es6/asyncQualifiedReturnType_es6.ts ===
+namespace X {
+>X : typeof X
+
+    export class MyPromise<T> extends Promise<T> {
+>MyPromise : MyPromise<T>
+>T : T
+>Promise : Promise<T>
+>T : T
+    }
+}
+
+async function f(): X.MyPromise<void> {
+>f : () => X.MyPromise<void>
+>X : any
+>MyPromise : X.MyPromise<T>
+}
diff --git a/tests/baselines/reference/awaitBinaryExpression1_es6.js b/tests/baselines/reference/awaitBinaryExpression1_es6.js
index a19e94353d595..8deb771f5abf2 100644
--- a/tests/baselines/reference/awaitBinaryExpression1_es6.js
+++ b/tests/baselines/reference/awaitBinaryExpression1_es6.js
@@ -9,7 +9,7 @@ async function func(): Promise<void> {
 
 //// [awaitBinaryExpression1_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = (yield p) || a;
         "after";
diff --git a/tests/baselines/reference/awaitBinaryExpression2_es6.js b/tests/baselines/reference/awaitBinaryExpression2_es6.js
index 7fb1a70446b26..506af50a0efba 100644
--- a/tests/baselines/reference/awaitBinaryExpression2_es6.js
+++ b/tests/baselines/reference/awaitBinaryExpression2_es6.js
@@ -9,7 +9,7 @@ async function func(): Promise<void> {
 
 //// [awaitBinaryExpression2_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = (yield p) && a;
         "after";
diff --git a/tests/baselines/reference/awaitBinaryExpression3_es6.js b/tests/baselines/reference/awaitBinaryExpression3_es6.js
index f845ce1242148..4b298d7b94751 100644
--- a/tests/baselines/reference/awaitBinaryExpression3_es6.js
+++ b/tests/baselines/reference/awaitBinaryExpression3_es6.js
@@ -9,7 +9,7 @@ async function func(): Promise<void> {
 
 //// [awaitBinaryExpression3_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = (yield p) + a;
         "after";
diff --git a/tests/baselines/reference/awaitBinaryExpression4_es6.js b/tests/baselines/reference/awaitBinaryExpression4_es6.js
index b6e14c8248761..4d31358898442 100644
--- a/tests/baselines/reference/awaitBinaryExpression4_es6.js
+++ b/tests/baselines/reference/awaitBinaryExpression4_es6.js
@@ -9,7 +9,7 @@ async function func(): Promise<void> {
 
 //// [awaitBinaryExpression4_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = yield p, a;
         "after";
diff --git a/tests/baselines/reference/awaitBinaryExpression5_es6.js b/tests/baselines/reference/awaitBinaryExpression5_es6.js
index 65a5bbfee777f..01d6c50f6f03e 100644
--- a/tests/baselines/reference/awaitBinaryExpression5_es6.js
+++ b/tests/baselines/reference/awaitBinaryExpression5_es6.js
@@ -10,7 +10,7 @@ async function func(): Promise<void> {
 
 //// [awaitBinaryExpression5_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var o;
         o.a = yield p;
diff --git a/tests/baselines/reference/awaitCallExpression1_es6.js b/tests/baselines/reference/awaitCallExpression1_es6.js
index aeeb598e3bf18..f9dad87a8b6b3 100644
--- a/tests/baselines/reference/awaitCallExpression1_es6.js
+++ b/tests/baselines/reference/awaitCallExpression1_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression1_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = fn(a, a, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression2_es6.js b/tests/baselines/reference/awaitCallExpression2_es6.js
index b41735275a842..87d99cd079399 100644
--- a/tests/baselines/reference/awaitCallExpression2_es6.js
+++ b/tests/baselines/reference/awaitCallExpression2_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression2_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = fn(yield p, a, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression3_es6.js b/tests/baselines/reference/awaitCallExpression3_es6.js
index 74dee3e7e427c..f397d83c3a14e 100644
--- a/tests/baselines/reference/awaitCallExpression3_es6.js
+++ b/tests/baselines/reference/awaitCallExpression3_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression3_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = fn(a, yield p, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression4_es6.js b/tests/baselines/reference/awaitCallExpression4_es6.js
index 682a1776ac53c..d8824d7e7a007 100644
--- a/tests/baselines/reference/awaitCallExpression4_es6.js
+++ b/tests/baselines/reference/awaitCallExpression4_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression4_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = (yield pfn)(a, a, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression5_es6.js b/tests/baselines/reference/awaitCallExpression5_es6.js
index 30889b350115f..f39a633765d88 100644
--- a/tests/baselines/reference/awaitCallExpression5_es6.js
+++ b/tests/baselines/reference/awaitCallExpression5_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression5_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = o.fn(a, a, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression6_es6.js b/tests/baselines/reference/awaitCallExpression6_es6.js
index 55d86119d6495..de8477fa9388a 100644
--- a/tests/baselines/reference/awaitCallExpression6_es6.js
+++ b/tests/baselines/reference/awaitCallExpression6_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression6_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = o.fn(yield p, a, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression7_es6.js b/tests/baselines/reference/awaitCallExpression7_es6.js
index df805266ff3a2..24edc3b9393e6 100644
--- a/tests/baselines/reference/awaitCallExpression7_es6.js
+++ b/tests/baselines/reference/awaitCallExpression7_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression7_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = o.fn(a, yield p, a);
         "after";
diff --git a/tests/baselines/reference/awaitCallExpression8_es6.js b/tests/baselines/reference/awaitCallExpression8_es6.js
index 8d7bb4b83ce96..8bee6112a7a39 100644
--- a/tests/baselines/reference/awaitCallExpression8_es6.js
+++ b/tests/baselines/reference/awaitCallExpression8_es6.js
@@ -13,7 +13,7 @@ async function func(): Promise<void> {
 
 //// [awaitCallExpression8_es6.js]
 function func() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
         "before";
         var b = (yield po).fn(a, a, a);
         "after";
diff --git a/tests/baselines/reference/noCustomAsyncReturnType_es6.errors.txt b/tests/baselines/reference/noCustomAsyncReturnType_es6.errors.txt
new file mode 100644
index 0000000000000..e3f70fb40cde4
--- /dev/null
+++ b/tests/baselines/reference/noCustomAsyncReturnType_es6.errors.txt
@@ -0,0 +1,16 @@
+tests/cases/conformance/async/es6/noCustomAsyncReturnType_es6.ts(3,5): error TS2529: Duplicate identifier 'Promise'. Compiler reserves name 'Promise' in top level scope of a module containing async functions.
+tests/cases/conformance/async/es6/noCustomAsyncReturnType_es6.ts(5,28): error TS1064: The return type of an async function or method must be the global Promise<T> type.
+
+
+==== tests/cases/conformance/async/es6/noCustomAsyncReturnType_es6.ts (2 errors) ====
+    
+    interface Promise<T> extends PromiseLike<T> {}
+    var Promise: PromiseConstructorLike;
+        ~~~~~~~
+!!! error TS2529: Duplicate identifier 'Promise'. Compiler reserves name 'Promise' in top level scope of a module containing async functions.
+    
+    export async function f(): Promise<void> {
+                               ~~~~~~~~~~~~~
+!!! error TS1064: The return type of an async function or method must be the global Promise<T> type.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/noCustomAsyncReturnType_es6.js b/tests/baselines/reference/noCustomAsyncReturnType_es6.js
new file mode 100644
index 0000000000000..05eb4afff39b0
--- /dev/null
+++ b/tests/baselines/reference/noCustomAsyncReturnType_es6.js
@@ -0,0 +1,23 @@
+//// [noCustomAsyncReturnType_es6.ts]
+
+interface Promise<T> extends PromiseLike<T> {}
+var Promise: PromiseConstructorLike;
+
+export async function f(): Promise<void> {
+}
+
+
+//// [noCustomAsyncReturnType_es6.js]
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator.throw(value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments)).next());
+    });
+};
+var Promise;
+export function f() {
+    return __awaiter(this, void 0, void 0, function* () {
+    });
+}
diff --git a/tests/baselines/reference/reachabilityChecks7.js b/tests/baselines/reference/reachabilityChecks7.js
index 0a6b5b0dac7b5..0f14eb697669f 100644
--- a/tests/baselines/reference/reachabilityChecks7.js
+++ b/tests/baselines/reference/reachabilityChecks7.js
@@ -50,7 +50,7 @@ let x = function () {
 };
 // async function with which promised type is void - return can be omitted
 function f2() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
     });
 }
 function f3(x) {
@@ -60,7 +60,7 @@ function f3(x) {
     });
 }
 function f4() {
-    return __awaiter(this, void 0, void 0, function* () {
+    return __awaiter(this, void 0, Promise, function* () {
     });
 }
 function voidFunc() {
diff --git a/tests/cases/conformance/async/es6/noCustomAsyncReturnType_es6.ts b/tests/cases/conformance/async/es6/noCustomAsyncReturnType_es6.ts
new file mode 100644
index 0000000000000..774cf6efab739
--- /dev/null
+++ b/tests/cases/conformance/async/es6/noCustomAsyncReturnType_es6.ts
@@ -0,0 +1,8 @@
+// @target: ES6
+// @noCustomAsyncPromise: true
+
+interface Promise<T> extends PromiseLike<T> {}
+var Promise: PromiseConstructorLike;
+
+export async function f(): Promise<void> {
+}