diff --git a/dom/workers/ServiceWorkerEvents.cpp b/dom/workers/ServiceWorkerEvents.cpp
index 436750babc7b..04d57bdde49f 100644
--- a/dom/workers/ServiceWorkerEvents.cpp
+++ b/dom/workers/ServiceWorkerEvents.cpp
@@ -408,6 +408,9 @@ FetchEvent::RespondWith(Promise& aArg, ErrorResult& aRv)
     return;
   }
 
+  if (!mPromise) {
+    mPromise = &aArg;
+  }
   nsRefPtr<InternalRequest> ir = mRequest->GetInternalRequest();
   mWaitToRespond = true;
   nsRefPtr<RespondWithHandler> handler =
@@ -440,7 +443,8 @@ NS_IMPL_RELEASE_INHERITED(FetchEvent, Event)
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(FetchEvent)
 NS_INTERFACE_MAP_END_INHERITING(Event)
 
-NS_IMPL_CYCLE_COLLECTION_INHERITED(FetchEvent, Event, mRequest, mClient)
+NS_IMPL_CYCLE_COLLECTION_INHERITED(FetchEvent, Event, mRequest, mClient,
+                                   mPromise)
 
 ExtendableEvent::ExtendableEvent(EventTarget* aOwner)
   : Event(aOwner, nullptr, nullptr)
diff --git a/dom/workers/ServiceWorkerEvents.h b/dom/workers/ServiceWorkerEvents.h
index dd8847f825c5..51e9d691bcbc 100644
--- a/dom/workers/ServiceWorkerEvents.h
+++ b/dom/workers/ServiceWorkerEvents.h
@@ -55,6 +55,7 @@ class FetchEvent final : public Event
   nsRefPtr<Request> mRequest;
   nsCString mScriptSpec;
   UniquePtr<ServiceWorkerClientInfo> mClientInfo;
+  nsRefPtr<Promise> mPromise;
   bool mIsReload;
   bool mWaitToRespond;
 protected:
@@ -105,6 +106,13 @@ public:
   void
   RespondWith(Promise& aArg, ErrorResult& aRv);
 
+  already_AddRefed<Promise>
+  GetPromise() const
+  {
+    nsRefPtr<Promise> p = mPromise;
+    return p.forget();
+  }
+
   already_AddRefed<Promise>
   ForwardTo(const nsAString& aUrl);
 
diff --git a/dom/workers/ServiceWorkerPrivate.cpp b/dom/workers/ServiceWorkerPrivate.cpp
index f0da36002202..f6f3f3b5622d 100644
--- a/dom/workers/ServiceWorkerPrivate.cpp
+++ b/dom/workers/ServiceWorkerPrivate.cpp
@@ -1068,6 +1068,12 @@ private:
       MOZ_ALWAYS_TRUE(NS_SUCCEEDED(NS_DispatchToMainThread(runnable)));
     }
 
+    nsRefPtr<Promise> respondWithPromise = event->GetPromise();
+    if (respondWithPromise) {
+      nsRefPtr<KeepAliveHandler> keepAliveHandler =
+        new KeepAliveHandler(mKeepAliveToken);
+      respondWithPromise->AppendNativeHandler(keepAliveHandler);
+    }
     return true;
   }
 };