diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends6.errors.txt b/tests/baselines/reference/declarationEmitExpressionInExtends6.errors.txt
index 9410f5af7f34d..acd1e1a7c9eeb 100644
--- a/tests/baselines/reference/declarationEmitExpressionInExtends6.errors.txt
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends6.errors.txt
@@ -10,6 +10,6 @@
 ==== /node_modules/@types/node/index.d.ts (0 errors) ====
     declare const require: any;
     
-==== /a.ts (0 errors) ====
+==== /a.js (0 errors) ====
     export class Foo {}
     
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends6.js b/tests/baselines/reference/declarationEmitExpressionInExtends6.js
index f7083c8bb8ac1..21506228d9966 100644
--- a/tests/baselines/reference/declarationEmitExpressionInExtends6.js
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends6.js
@@ -3,7 +3,7 @@
 //// [index.d.ts]
 declare const require: any;
 
-//// [a.ts]
+//// [a.js]
 export class Foo {}
 
 //// [b.ts]
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends7.errors.txt b/tests/baselines/reference/declarationEmitExpressionInExtends7.errors.txt
new file mode 100644
index 0000000000000..0cfcdc81dfb2b
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends7.errors.txt
@@ -0,0 +1,11 @@
+tests/cases/compiler/declarationEmitExpressionInExtends7.ts(1,30): error TS2304: Cannot find name 'SomeUndefinedFunction'.
+tests/cases/compiler/declarationEmitExpressionInExtends7.ts(1,30): error TS4021: 'extends' clause of exported class has or is using private name 'SomeUndefinedFunction'.
+
+
+==== tests/cases/compiler/declarationEmitExpressionInExtends7.ts (2 errors) ====
+    export default class extends SomeUndefinedFunction {}
+                                 ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2304: Cannot find name 'SomeUndefinedFunction'.
+                                 ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS4021: 'extends' clause of exported class has or is using private name 'SomeUndefinedFunction'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends7.js b/tests/baselines/reference/declarationEmitExpressionInExtends7.js
new file mode 100644
index 0000000000000..ef0809bda84c0
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends7.js
@@ -0,0 +1,28 @@
+//// [declarationEmitExpressionInExtends7.ts]
+export default class extends SomeUndefinedFunction {}
+
+
+//// [declarationEmitExpressionInExtends7.js]
+"use strict";
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = function (d, b) {
+        extendStatics = Object.setPrototypeOf ||
+            ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+            function (d, b) { for (var p in b) if (Object.prototype.hasOwnProperty.call(b, p)) d[p] = b[p]; };
+        return extendStatics(d, b);
+    };
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+exports.__esModule = true;
+var default_1 = /** @class */ (function (_super) {
+    __extends(default_1, _super);
+    function default_1() {
+        return _super !== null && _super.apply(this, arguments) || this;
+    }
+    return default_1;
+}(SomeUndefinedFunction));
+exports["default"] = default_1;
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends7.symbols b/tests/baselines/reference/declarationEmitExpressionInExtends7.symbols
new file mode 100644
index 0000000000000..a81c2cc3871ee
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends7.symbols
@@ -0,0 +1,4 @@
+=== tests/cases/compiler/declarationEmitExpressionInExtends7.ts ===
+export default class extends SomeUndefinedFunction {}
+No type information for this code.
+No type information for this code.
\ No newline at end of file
diff --git a/tests/baselines/reference/declarationEmitExpressionInExtends7.types b/tests/baselines/reference/declarationEmitExpressionInExtends7.types
new file mode 100644
index 0000000000000..5a018ac590f12
--- /dev/null
+++ b/tests/baselines/reference/declarationEmitExpressionInExtends7.types
@@ -0,0 +1,4 @@
+=== tests/cases/compiler/declarationEmitExpressionInExtends7.ts ===
+export default class extends SomeUndefinedFunction {}
+>SomeUndefinedFunction : any
+
diff --git a/tests/cases/compiler/declarationEmitExpressionInExtends6.ts b/tests/cases/compiler/declarationEmitExpressionInExtends6.ts
index 057d1cabf0224..876be6ded3c9b 100644
--- a/tests/cases/compiler/declarationEmitExpressionInExtends6.ts
+++ b/tests/cases/compiler/declarationEmitExpressionInExtends6.ts
@@ -1,12 +1,13 @@
 // @module: commonjs
 // @declaration: true
+// @allowJs: true
 // @types: node
 // @currentDirectory: /
 
 // @Filename: /node_modules/@types/node/index.d.ts
 declare const require: any;
 
-// @Filename: /a.ts
+// @Filename: /a.js
 export class Foo {}
 
 // @Filename: /b.ts
diff --git a/tests/cases/compiler/declarationEmitExpressionInExtends7.ts b/tests/cases/compiler/declarationEmitExpressionInExtends7.ts
new file mode 100644
index 0000000000000..8ec46fe1524ae
--- /dev/null
+++ b/tests/cases/compiler/declarationEmitExpressionInExtends7.ts
@@ -0,0 +1,2 @@
+// @declaration: true
+export default class extends SomeUndefinedFunction {}