--- a/dom/media/MediaManager.cpp
+++ b/dom/media/MediaManager.cpp
@@ -1697,30 +1697,32 @@ MediaManager::EnumerateRawDevices(uint64
     if (aVideoType == MediaSourceEnum::Camera) {
       Preferences::GetCString("media.video_loopback_dev", videoLoopDev);
     }
     if (aAudioType == MediaSourceEnum::Microphone) {
       Preferences::GetCString("media.audio_loopback_dev", audioLoopDev);
     }
   }
 
+  bool hasVideo = aVideoType != MediaSourceEnum::Other;
+  bool hasAudio = aAudioType != MediaSourceEnum::Other;
+  bool fakeCams = aFake && aVideoType == MediaSourceEnum::Camera;
+  bool fakeMics = aFake && aAudioType == MediaSourceEnum::Microphone;
+  bool realDevicesRequested = (!fakeCams && hasVideo) || (!fakeMics && hasAudio);
+
   RefPtr<Runnable> task = NewTaskFrom([id, aWindowId, audioLoopDev,
                                        videoLoopDev, aVideoType,
-                                       aAudioType, aFake]() mutable {
+                                       aAudioType, hasVideo, hasAudio,
+                                       fakeCams, fakeMics, realDevicesRequested]() {
     // Only enumerate what's asked for, and only fake cams and mics.
-    bool hasVideo = aVideoType != MediaSourceEnum::Other;
-    bool hasAudio = aAudioType != MediaSourceEnum::Other;
-    bool fakeCams = aFake && aVideoType == MediaSourceEnum::Camera;
-    bool fakeMics = aFake && aAudioType == MediaSourceEnum::Microphone;
-
     RefPtr<MediaEngine> fakeBackend, realBackend;
     if (fakeCams || fakeMics) {
       fakeBackend = new MediaEngineDefault();
     }
-    if ((!fakeCams && hasVideo) || (!fakeMics && hasAudio)) {
+    if (realDevicesRequested) {
       MediaManager* manager = MediaManager::GetIfExists();
       MOZ_RELEASE_ASSERT(manager); // Must exist while media thread is alive
       realBackend = manager->GetBackend(aWindowId);
       // We need to listen to this event even JS didn't listen to it.
       realBackend->AddDeviceChangeCallback(manager);
     }
 
     auto result = MakeUnique<SourceSet>();
@@ -1753,19 +1755,17 @@ MediaManager::EnumerateRawDevices(uint64
       RefPtr<PledgeSourceSet> p = mgr->mOutstandingPledges.Remove(id);
       if (p) {
         p->Resolve(result.release());
       }
       return NS_OK;
     }));
   });
 
-  if (!aFake &&
-      (aVideoType == MediaSourceEnum::Camera ||
-       aAudioType == MediaSourceEnum::Microphone) &&
+  if (realDevicesRequested &&
       Preferences::GetBool("media.navigator.permission.device", false)) {
     // Need to ask permission to retrieve list of all devices;
     // notify frontend observer and wait for callback notification to post task.
     const char16_t* const type =
       (aVideoType != MediaSourceEnum::Camera)     ? u"audio" :
       (aAudioType != MediaSourceEnum::Microphone) ? u"video" :
                                                     u"all";
     nsCOMPtr<nsIObserverService> obs = services::GetObserverService();