--- a/dom/messagechannel/MessagePort.cpp
+++ b/dom/messagechannel/MessagePort.cpp
@@ -292,18 +292,18 @@ MessagePort::Initialize(const nsID& aUUI
     MOZ_ASSERT(workerPrivate);
 
     // When the callback is executed, we cannot process messages anymore because
     // we cannot dispatch new runnables. Let's force a Close().
     RefPtr<StrongWorkerRef> strongWorkerRef =
       StrongWorkerRef::Create(workerPrivate, "MessagePort",
                               [self]() { self->CloseForced(); });
     if (NS_WARN_IF(!strongWorkerRef)) {
-      // The worker is shutting down. Let's return an already closed port.
-      mState = eStateDisentangledForClose;
+      // The worker is shutting down.
+      aRv.Throw(NS_ERROR_FAILURE);
       return;
     }
 
     MOZ_ASSERT(!mWorkerRef);
     mWorkerRef = Move(strongWorkerRef);
   } else if (GetOwner()) {
     MOZ_ASSERT(NS_IsMainThread());
     mInnerID = GetOwner()->WindowID();

--- a/dom/workers/WorkerRef.cpp
+++ b/dom/workers/WorkerRef.cpp
@@ -65,16 +65,20 @@ public:
     , mWorkerRef(aWorkerRef)
   {}
 
   bool
   Notify(WorkerStatus aStatus) override
   {
     MOZ_ASSERT(mWorkerRef);
 
+    if (aStatus < Canceling) {
+      return true;
+    }
+
     // Let's keep this object alive for the whole Notify() execution.
     RefPtr<WorkerRef> workerRef;
     workerRef = mWorkerRef;
 
     workerRef->Notify();
     return true;
   }
 
@@ -123,17 +127,17 @@ WeakWorkerRef::Create(WorkerPrivate* aWo
   MOZ_ASSERT(aWorkerPrivate);
   aWorkerPrivate->AssertIsOnWorkerThread();
 
   RefPtr<WeakWorkerRef> ref = new WeakWorkerRef(aWorkerPrivate);
 
   // This holder doesn't keep the worker alive.
   UniquePtr<Holder> holder(new Holder("WeakWorkerRef::Holder", ref,
                                       WorkerHolder::AllowIdleShutdownStart));
-  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Closing))) {
+  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Canceling))) {
     return nullptr;
   }
 
   ref->mHolder = Move(holder);
   ref->mCallback = aCallback;
 
   return ref.forget();
 }
@@ -177,17 +181,17 @@ StrongWorkerRef::Create(WorkerPrivate* a
   MOZ_ASSERT(aWorkerPrivate);
   MOZ_ASSERT(aName);
 
   RefPtr<StrongWorkerRef> ref = new StrongWorkerRef(aWorkerPrivate);
 
   // The worker is kept alive by this holder.
   UniquePtr<Holder> holder(new Holder(aName, ref,
                                       WorkerHolder::PreventIdleShutdownStart));
-  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Closing))) {
+  if (NS_WARN_IF(!holder->HoldWorker(aWorkerPrivate, Canceling))) {
     return nullptr;
   }
 
   ref->mHolder = Move(holder);
   ref->mCallback = aCallback;
 
   return ref.forget();
 }