diff --git a/modules/@angular/core/package.json b/modules/@angular/core/package.json
index c29fdfdeba..88d85bee83 100644
--- a/modules/@angular/core/package.json
+++ b/modules/@angular/core/package.json
@@ -9,7 +9,7 @@
   "license": "MIT",
   "peerDependencies": {
     "rxjs": "5.0.0-beta.11",
-    "zone.js": "^0.6.17"
+    "zone.js": "^0.6.21"
   },
   "repository": {
     "type": "git",
diff --git a/modules/@angular/core/src/zone/ng_zone_impl.ts b/modules/@angular/core/src/zone/ng_zone_impl.ts
index 5c432a25f7..3d636e98ad 100644
--- a/modules/@angular/core/src/zone/ng_zone_impl.ts
+++ b/modules/@angular/core/src/zone/ng_zone_impl.ts
@@ -35,62 +35,61 @@ export class NgZoneImpl {
     this.setMacrotask = setMacrotask;
     this.onError = onError;
 
-    if (Zone) {
-      this.outer = this.inner = Zone.current;
-      if ((Zone as any /** TODO #9100 */)['wtfZoneSpec']) {
-        this.inner = this.inner.fork((Zone as any /** TODO #9100 */)['wtfZoneSpec']);
-      }
-      if (trace && (Zone as any /** TODO #9100 */)['longStackTraceZoneSpec']) {
-        this.inner = this.inner.fork((Zone as any /** TODO #9100 */)['longStackTraceZoneSpec']);
-      }
-      this.inner = this.inner.fork({
-        name: 'angular',
-        properties: <any>{'isAngularZone': true},
-        onInvokeTask: (delegate: ZoneDelegate, current: Zone, target: Zone, task: Task,
-                       applyThis: any, applyArgs: any): any => {
-          try {
-            this.onEnter();
-            return delegate.invokeTask(target, task, applyThis, applyArgs);
-          } finally {
-            this.onLeave();
-          }
-        },
-
-
-        onInvoke: (delegate: ZoneDelegate, current: Zone, target: Zone, callback: Function,
-                   applyThis: any, applyArgs: any[], source: string): any => {
-          try {
-            this.onEnter();
-            return delegate.invoke(target, callback, applyThis, applyArgs, source);
-          } finally {
-            this.onLeave();
-          }
-        },
-
-        onHasTask:
-            (delegate: ZoneDelegate, current: Zone, target: Zone, hasTaskState: HasTaskState) => {
-              delegate.hasTask(target, hasTaskState);
-              if (current == target) {
-                // We are only interested in hasTask events which originate from our zone
-                // (A child hasTask event is not interesting to us)
-                if (hasTaskState.change == 'microTask') {
-                  this.setMicrotask(hasTaskState.microTask);
-                } else if (hasTaskState.change == 'macroTask') {
-                  this.setMacrotask(hasTaskState.macroTask);
-                }
-              }
-            },
-
-        onHandleError: (delegate: ZoneDelegate, current: Zone, target: Zone, error: any):
-                           boolean => {
-                             delegate.handleError(target, error);
-                             this.onError(error);
-                             return false;
-                           }
-      });
-    } else {
-      throw new Error('Angular requires Zone.js polyfill.');
+    if (typeof Zone == 'undefined') {
+      throw new Error('Angular requires Zone.js prolyfill.');
     }
+    Zone.assertZonePatched();
+    this.outer = this.inner = Zone.current;
+    if ((Zone as any)['wtfZoneSpec']) {
+      this.inner = this.inner.fork((Zone as any)['wtfZoneSpec']);
+    }
+    if (trace && (Zone as any)['longStackTraceZoneSpec']) {
+      this.inner = this.inner.fork((Zone as any)['longStackTraceZoneSpec']);
+    }
+    this.inner = this.inner.fork({
+      name: 'angular',
+      properties: <any>{'isAngularZone': true},
+      onInvokeTask: (delegate: ZoneDelegate, current: Zone, target: Zone, task: Task,
+                     applyThis: any, applyArgs: any): any => {
+        try {
+          this.onEnter();
+          return delegate.invokeTask(target, task, applyThis, applyArgs);
+        } finally {
+          this.onLeave();
+        }
+      },
+
+
+      onInvoke: (delegate: ZoneDelegate, current: Zone, target: Zone, callback: Function,
+                 applyThis: any, applyArgs: any[], source: string): any => {
+        try {
+          this.onEnter();
+          return delegate.invoke(target, callback, applyThis, applyArgs, source);
+        } finally {
+          this.onLeave();
+        }
+      },
+
+      onHasTask:
+          (delegate: ZoneDelegate, current: Zone, target: Zone, hasTaskState: HasTaskState) => {
+            delegate.hasTask(target, hasTaskState);
+            if (current === target) {
+              // We are only interested in hasTask events which originate from our zone
+              // (A child hasTask event is not interesting to us)
+              if (hasTaskState.change == 'microTask') {
+                this.setMicrotask(hasTaskState.microTask);
+              } else if (hasTaskState.change == 'macroTask') {
+                this.setMacrotask(hasTaskState.macroTask);
+              }
+            }
+          },
+
+      onHandleError: (delegate: ZoneDelegate, current: Zone, target: Zone, error: any): boolean => {
+        delegate.handleError(target, error);
+        this.onError(error);
+        return false;
+      }
+    });
   }
 
   runInner(fn: () => any): any { return this.inner.run(fn); };
diff --git a/npm-shrinkwrap.clean.json b/npm-shrinkwrap.clean.json
index 17322318fc..bec21d7683 100644
--- a/npm-shrinkwrap.clean.json
+++ b/npm-shrinkwrap.clean.json
@@ -4655,7 +4655,7 @@
       }
     },
     "zone.js": {
-      "version": "0.6.17"
+      "version": "0.6.21"
     }
   },
   "name": "angular-srcs",
diff --git a/npm-shrinkwrap.json b/npm-shrinkwrap.json
index ea5fcf15a5..063850945d 100644
--- a/npm-shrinkwrap.json
+++ b/npm-shrinkwrap.json
@@ -7421,9 +7421,8 @@
       }
     },
     "zone.js": {
-      "version": "0.6.17",
-      "from": "zone.js@0.6.17",
-      "resolved": "https://registry.npmjs.org/zone.js/-/zone.js-0.6.17.tgz"
+      "version": "0.6.21",
+      "from": "zone.js@0.6.21"
     }
   }
 }
diff --git a/package.json b/package.json
index add792e79b..c3f7adf771 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,7 @@
     "core-js": "^2.4.1",
     "reflect-metadata": "^0.1.3",
     "rxjs": "5.0.0-beta.11",
-    "zone.js": "^0.6.17"
+    "zone.js": "^0.6.21"
   },
   "devDependencies": {
     "@types/angularjs": "^1.5.13-alpha",
diff --git a/scripts/ci-lite/offline_compiler_test.sh b/scripts/ci-lite/offline_compiler_test.sh
index 96eb76b170..bc3ffdac5c 100755
--- a/scripts/ci-lite/offline_compiler_test.sh
+++ b/scripts/ci-lite/offline_compiler_test.sh
@@ -9,7 +9,7 @@ LINKABLE_PKGS=(
 PKGS=(
   reflect-metadata@0.1.8
   typescript@2.0.2
-  zone.js@0.6.17
+  zone.js@0.6.21
   rxjs@5.0.0-beta.11
   @types/{node@6.0.38,jasmine@2.2.33}
   jasmine@2.4.1