diff --git a/lib/browser/event-target-legacy.ts b/lib/browser/event-target-legacy.ts
index 9a4b025ef..420ffb2af 100644
--- a/lib/browser/event-target-legacy.ts
+++ b/lib/browser/event-target-legacy.ts
@@ -24,7 +24,7 @@ export function eventTargetLegacyPatch(_global: any, api: _ZonePrivate) {
     // Workaround for: https://github.com/google/tracing-framework/issues/555
     apis = WTF_ISSUE_555_ARRAY.map((v) => 'HTML' + v + 'Element').concat(NO_EVENT_TARGET);
   } else if (_global[EVENT_TARGET]) {
-    // EventTarget is already patched in browser.ts
+    apis.push(EVENT_TARGET);
   } else {
     // Note: EventTarget is not available in all browsers,
     // if it's not available, we instead patch the APIs in the IDL that inherit from EventTarget
@@ -101,7 +101,7 @@ export function eventTargetLegacyPatch(_global: any, api: _ZonePrivate) {
   // vh is validateHandler to check event handler
   // is valid or not(for security check)
   api.patchEventTarget(_global, apiTypes, {vh: checkIEAndCrossContext});
-
+  (Zone as any)[api.symbol('patchEventTarget')] = !!_global[EVENT_TARGET];
   return true;
 }
 
diff --git a/lib/browser/event-target.ts b/lib/browser/event-target.ts
index abbe51837..525f52976 100644
--- a/lib/browser/event-target.ts
+++ b/lib/browser/event-target.ts
@@ -7,6 +7,10 @@
  */
 
 export function eventTargetPatch(_global: any, api: _ZonePrivate) {
+  if ((Zone as any)[api.symbol('patchEventTarget')]) {
+    // EventTarget is already patched.
+    return;
+  }
   const {eventNames, zoneSymbolEventNames, TRUE_STR, FALSE_STR, ZONE_SYMBOL_PREFIX} =
       api.getGlobalObjects()!;
   //  predefine all __zone_symbol__ + eventName + true/false string