diff --git a/src/compiler/transformers/es5.ts b/src/compiler/transformers/es5.ts
index f051aac98f4..6dd875965d9 100644
--- a/src/compiler/transformers/es5.ts
+++ b/src/compiler/transformers/es5.ts
@@ -63,7 +63,7 @@ namespace ts {
          * @param node The node to substitute.
          */
         function onSubstituteNode(emitContext: EmitContext, node: Node) {
-            if (node.id && noSubstitution[node.id]) {
+            if (node.id && noSubstitution && noSubstitution[node.id]) {
                 return previousOnSubstituteNode(emitContext, node);
             }