diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d58ad9fbf9a..bab573c8b7f 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7936,7 +7936,7 @@ namespace ts {
             const declaration = localOrExportSymbol.valueDeclaration;
             const defaultsToDeclaredType = !strictNullChecks || !declaration ||
                 declaration.kind === SyntaxKind.Parameter || isInAmbientContext(declaration) ||
-                getContainingFunction(declaration) !== getContainingFunction(node);
+                getContainingFunctionOrSourceFile(declaration) !== getContainingFunctionOrSourceFile(node);
             if (defaultsToDeclaredType && !(type.flags & TypeFlags.Narrowable)) {
                 return type;
             }
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 638c7a60aa1..2e51f6a1504 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -840,6 +840,15 @@ namespace ts {
         }
     }
 
+    export function getContainingFunctionOrSourceFile(node: Node): FunctionLikeDeclaration | SourceFile {
+        while (true) {
+            node = node.parent;
+            if (isFunctionLike(node) || node.kind === SyntaxKind.SourceFile) {
+                return <FunctionLikeDeclaration | SourceFile>node;
+            }
+        }
+    }
+
     export function getContainingClass(node: Node): ClassLikeDeclaration {
         while (true) {
             node = node.parent;