diff --git a/modules/angular2/src/core/zone/ng_zone_impl.ts b/modules/angular2/src/core/zone/ng_zone_impl.ts
index 96ef145837..e9d513202d 100644
--- a/modules/angular2/src/core/zone/ng_zone_impl.ts
+++ b/modules/angular2/src/core/zone/ng_zone_impl.ts
@@ -41,7 +41,7 @@ export class NgZoneImpl {
       if (Zone['wtfZoneSpec']) {
         this.inner = this.inner.fork(Zone['wtfZoneSpec']);
       }
-      if (trace) {
+      if (trace && Zone['longStackTraceZoneSpec']) {
         this.inner = this.inner.fork(Zone['longStackTraceZoneSpec']);
       }
       this.inner = this.inner.fork({