diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ebe6693eb4..686efaa758 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -18100,7 +18100,7 @@ namespace ts {
 
             const baseTypeNode = getClassExtendsHeritageClauseElement(node);
             if (baseTypeNode) {
-                if (languageVersion < ScriptTarget.ES2015) {
+                if (languageVersion < ScriptTarget.ES2015 && !isInAmbientContext(node)) {
                     checkExternalEmitHelpers(baseTypeNode.parent, ExternalEmitHelpers.Extends);
                 }
 
diff --git a/tests/baselines/reference/importHelpersDeclarations.symbols b/tests/baselines/reference/importHelpersDeclarations.symbols
new file mode 100644
index 0000000000..f578850cc4
--- /dev/null
+++ b/tests/baselines/reference/importHelpersDeclarations.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/declaration.d.ts ===
+export declare class D {
+>D : Symbol(D, Decl(declaration.d.ts, 0, 0))
+}
+export declare class E extends D {
+>E : Symbol(E, Decl(declaration.d.ts, 1, 1))
+>D : Symbol(D, Decl(declaration.d.ts, 0, 0))
+}
diff --git a/tests/baselines/reference/importHelpersDeclarations.types b/tests/baselines/reference/importHelpersDeclarations.types
new file mode 100644
index 0000000000..4b8c56d786
--- /dev/null
+++ b/tests/baselines/reference/importHelpersDeclarations.types
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/declaration.d.ts ===
+export declare class D {
+>D : D
+}
+export declare class E extends D {
+>E : E
+>D : D
+}
diff --git a/tests/cases/compiler/importHelpersDeclarations.ts b/tests/cases/compiler/importHelpersDeclarations.ts
new file mode 100644
index 0000000000..7b958cda78
--- /dev/null
+++ b/tests/cases/compiler/importHelpersDeclarations.ts
@@ -0,0 +1,9 @@
+// @importHelpers: true
+// @target: es5
+// @module: commonjs
+// @moduleResolution: classic
+// @filename: declaration.d.ts
+export declare class D {
+}
+export declare class E extends D {
+}
\ No newline at end of file