--- a/dom/media/DOMMediaStream.cpp
+++ b/dom/media/DOMMediaStream.cpp
@@ -167,17 +167,18 @@ public:
       nsPIDOMWindowInner* window = mStream->GetParentObject();
       nsIDocument* doc = window ? window->GetExtantDoc() : nullptr;
       nsIPrincipal* principal = doc ? doc->NodePrincipal() : nullptr;
       source = new BasicUnstoppableTrackSource(principal);
     }
 
     RefPtr<MediaStreamTrack> newTrack =
       mStream->CreateDOMTrack(aTrackID, aType, source);
-    mStream->AddTrackInternal(newTrack);
+    NS_DispatchToMainThread(NewRunnableMethod<RefPtr<MediaStreamTrack>>(
+        mStream, &DOMMediaStream::AddTrackInternal, newTrack));
   }
 
   void DoNotifyTrackEnded(MediaStream* aInputStream, TrackID aInputTrackID,
                           TrackID aTrackID)
   {
     MOZ_ASSERT(NS_IsMainThread());
 
     if (!mStream) {
@@ -274,17 +275,21 @@ public:
   void DoNotifyFinishedTrackCreation()
   {
     MOZ_ASSERT(NS_IsMainThread());
 
     if (!mStream) {
       return;
     }
 
-    mStream->NotifyTracksCreated();
+    // The owned stream listener adds its tracks after another main thread
+    // dispatch. We have to do the same to notify of created tracks to stay
+    // in sync. (Or NotifyTracksCreated is called before tracks are added).
+    NS_DispatchToMainThread(
+        NewRunnableMethod(mStream, &DOMMediaStream::NotifyTracksCreated));
   }
 
   // The methods below are called on the MediaStreamGraph thread.
 
   void NotifyQueuedTrackChanges(MediaStreamGraph* aGraph, TrackID aID,
                                 StreamTime aTrackOffset, TrackEventCommand aTrackEvents,
                                 const MediaSegment& aQueuedMedia,
                                 MediaStream* aInputStream,