diff --git a/dom/workers/ServiceWorkerManager.cpp b/dom/workers/ServiceWorkerManager.cpp
index e5f66ff2fb28..77beae0f4853 100644
--- a/dom/workers/ServiceWorkerManager.cpp
+++ b/dom/workers/ServiceWorkerManager.cpp
@@ -1933,10 +1933,6 @@ void
 ServiceWorkerManager::MaybeStartControlling(nsIDocument* aDoc)
 {
   AssertIsOnMainThread();
-  if (!Preferences::GetBool("dom.serviceWorkers.enabled")) {
-    return;
-  }
-
   nsRefPtr<ServiceWorkerRegistrationInfo> registration =
     GetServiceWorkerRegistrationInfo(aDoc);
   if (registration) {
@@ -1948,14 +1944,35 @@ ServiceWorkerManager::MaybeStartControlling(nsIDocument* aDoc)
   }
 }
 
+class ServiceWorkerActivateAfterUnloadingJob MOZ_FINAL : public ServiceWorkerJob
+{
+  nsRefPtr<ServiceWorkerRegistrationInfo> mRegistration;
+public:
+  ServiceWorkerActivateAfterUnloadingJob(ServiceWorkerJobQueue* aQueue,
+                                         ServiceWorkerRegistrationInfo* aReg)
+    : ServiceWorkerJob(aQueue)
+    , mRegistration(aReg)
+  { }
+
+  void
+  Start()
+  {
+    if (mRegistration->mPendingUninstall) {
+      mRegistration->Clear();
+      nsRefPtr<ServiceWorkerManager> swm = ServiceWorkerManager::GetInstance();
+      swm->RemoveRegistration(mRegistration);
+    } else {
+      mRegistration->TryToActivate();
+    }
+
+    Done(NS_OK);
+  }
+};
+
 void
 ServiceWorkerManager::MaybeStopControlling(nsIDocument* aDoc)
 {
   MOZ_ASSERT(aDoc);
-  if (!Preferences::GetBool("dom.serviceWorkers.enabled")) {
-    return;
-  }
-
   nsRefPtr<ServiceWorkerRegistrationInfo> registration;
   mControlledDocuments.Remove(aDoc, getter_AddRefs(registration));
   // A document which was uncontrolled does not maintain that state itself, so
@@ -1963,6 +1980,14 @@ ServiceWorkerManager::MaybeStopControlling(nsIDocument* aDoc)
   // associated registration. So this check is required.
   if (registration) {
     registration->StopControllingADocument();
+    if (!registration->IsControllingDocuments()) {
+      ServiceWorkerJobQueue* queue = GetOrCreateJobQueue(registration->mScope);
+      // The remaining tasks touch registration->mPendingUninstall, so queue
+      // them up in a job.
+      nsRefPtr<ServiceWorkerActivateAfterUnloadingJob> job =
+        new ServiceWorkerActivateAfterUnloadingJob(queue, registration);
+      queue->Append(job);
+    }
   }
 }
 
diff --git a/dom/workers/ServiceWorkerManager.h b/dom/workers/ServiceWorkerManager.h
index e9c92be64792..0fc0bf6e6372 100644
--- a/dom/workers/ServiceWorkerManager.h
+++ b/dom/workers/ServiceWorkerManager.h
@@ -290,12 +290,13 @@ class ServiceWorkerManager MOZ_FINAL
   , public nsIIPCBackgroundChildCreateCallback
 {
   friend class ActivationRunnable;
-  friend class ServiceWorkerRegistrationInfo;
-  friend class ServiceWorkerRegisterJob;
   friend class GetReadyPromiseRunnable;
   friend class GetRegistrationsRunnable;
   friend class GetRegistrationRunnable;
   friend class QueueFireUpdateFoundRunnable;
+  friend class ServiceWorkerActivateAfterUnloadingJob;
+  friend class ServiceWorkerRegisterJob;
+  friend class ServiceWorkerRegistrationInfo;
   friend class ServiceWorkerUnregisterJob;
 
 public:
@@ -349,6 +350,8 @@ public:
   void
   RemoveRegistration(ServiceWorkerRegistrationInfo* aRegistration)
   {
+    MOZ_ASSERT(aRegistration);
+    MOZ_ASSERT(!aRegistration->IsControllingDocuments());
     MOZ_ASSERT(mServiceWorkerRegistrationInfos.Contains(aRegistration->mScope));
     ServiceWorkerManager::RemoveScope(mOrderedScopes, aRegistration->mScope);
     mServiceWorkerRegistrationInfos.Remove(aRegistration->mScope);
diff --git a/dom/workers/test/serviceworkers/test_installation_simple.html b/dom/workers/test/serviceworkers/test_installation_simple.html
index c0fc0ef3483b..42de8b905e9e 100644
--- a/dom/workers/test/serviceworkers/test_installation_simple.html
+++ b/dom/workers/test/serviceworkers/test_installation_simple.html
@@ -140,8 +140,7 @@
         window.onmessage = null;
         // We have to make frame navigate away, otherwise it will call
         // MaybeStopControlling() when this document is unloaded. At that point
-        // the pref has been disabled, and so MaybeStopControlling() will just
-        // return since it is currently gated.
+        // the pref has been disabled, so the ServiceWorkerManager is not available.
         frame.setAttribute("src", new URL("about:blank").href);
         resolve();
       } else if (e.data.type == "check") {