diff --git a/dom/serviceworkers/ServiceWorkerRegistration.cpp b/dom/serviceworkers/ServiceWorkerRegistration.cpp
index a2afd2b08f45..c867c28a9a49 100644
--- a/dom/serviceworkers/ServiceWorkerRegistration.cpp
+++ b/dom/serviceworkers/ServiceWorkerRegistration.cpp
@@ -523,13 +523,18 @@ void ServiceWorkerRegistration::WhenVersionReached(
 void ServiceWorkerRegistration::MaybeScheduleUpdateFound(
     const Maybe<ServiceWorkerDescriptor>& aInstallingDescriptor) {
   // This function sets mScheduledUpdateFoundId to note when we were told about
-  // a new installing worker. We rely on a call to
-  // MaybeDispatchUpdateFoundRunnable (called indirectly from UpdateJobCallback)
-  // to actually fire the event.
+  // a new installing worker. We rely on a call to MaybeDispatchUpdateFound via
+  // ServiceWorkerRegistrationChild::RecvFireUpdateFound to trigger the properly
+  // timed notification...
   uint64_t newId = aInstallingDescriptor.isSome()
                        ? aInstallingDescriptor.ref().Id()
                        : kInvalidUpdateFoundId;
 
+  // ...but the whole reason this logic exists is because SWRegistrations are
+  // bootstrapped off of inherently stale descriptor snapshots and receive
+  // catch-up updates once the actor is created and registered in the parent.
+  // To handle the catch-up case where we need to generate a synthetic
+  // updatefound that would otherwise be lost, we immediately flush here.
   if (mScheduledUpdateFoundId != kInvalidUpdateFoundId) {
     if (mScheduledUpdateFoundId == newId) {
       return;
@@ -548,22 +553,6 @@ void ServiceWorkerRegistration::MaybeScheduleUpdateFound(
   mScheduledUpdateFoundId = newId;
 }
 
-void ServiceWorkerRegistration::MaybeDispatchUpdateFoundRunnable() {
-  if (mScheduledUpdateFoundId == kInvalidUpdateFoundId) {
-    return;
-  }
-
-  nsIGlobalObject* global = GetParentObject();
-  NS_ENSURE_TRUE_VOID(global);
-
-  nsCOMPtr<nsIRunnable> r = NewCancelableRunnableMethod(
-      "ServiceWorkerRegistration::MaybeDispatchUpdateFound", this,
-      &ServiceWorkerRegistration::MaybeDispatchUpdateFound);
-
-  Unused << global->SerialEventTarget()->Dispatch(r.forget(),
-                                                  NS_DISPATCH_NORMAL);
-}
-
 void ServiceWorkerRegistration::MaybeDispatchUpdateFound() {
   uint64_t scheduledId = mScheduledUpdateFoundId;
   mScheduledUpdateFoundId = kInvalidUpdateFoundId;
diff --git a/dom/serviceworkers/ServiceWorkerRegistration.h b/dom/serviceworkers/ServiceWorkerRegistration.h
index fa638d37b656..c354e3e138f1 100644
--- a/dom/serviceworkers/ServiceWorkerRegistration.h
+++ b/dom/serviceworkers/ServiceWorkerRegistration.h
@@ -105,11 +105,9 @@ class ServiceWorkerRegistration final : public DOMEventTargetHelper {
   void WhenVersionReached(uint64_t aVersion,
                           ServiceWorkerBoolCallback&& aCallback);
 
-  void MaybeDispatchUpdateFoundRunnable();
-
   void RevokeActor(ServiceWorkerRegistrationChild* aActor);
 
-  void FireUpdateFound();
+  void FireUpdateFound() { MaybeDispatchUpdateFound(); }
 
  private:
   ServiceWorkerRegistration(
diff --git a/dom/serviceworkers/ServiceWorkerRegistrationChild.cpp b/dom/serviceworkers/ServiceWorkerRegistrationChild.cpp
index b382f6dcfaf9..d3ed8c4cbd98 100644
--- a/dom/serviceworkers/ServiceWorkerRegistrationChild.cpp
+++ b/dom/serviceworkers/ServiceWorkerRegistrationChild.cpp
@@ -34,7 +34,7 @@ IPCResult ServiceWorkerRegistrationChild::RecvUpdateState(
 
 IPCResult ServiceWorkerRegistrationChild::RecvFireUpdateFound() {
   if (mOwner) {
-    mOwner->MaybeDispatchUpdateFoundRunnable();
+    mOwner->FireUpdateFound();
   }
   return IPC_OK();
 }