diff --git a/src/compiler/transformer.ts b/src/compiler/transformer.ts
index 45b2ba0ee2..9edecce89e 100644
--- a/src/compiler/transformer.ts
+++ b/src/compiler/transformer.ts
@@ -69,9 +69,7 @@ namespace ts {
             }
 
             currentSourceFile = sourceFile;
-            const visited = transformation(sourceFile);
-            currentSourceFile = undefined;
-            return visited;
+            return transformation(sourceFile);
         }
 
         function enableExpressionSubstitution(kind: SyntaxKind) {