diff --git a/dom/media/MediaStreamGraph.cpp b/dom/media/MediaStreamGraph.cpp
index 9d8c87bef6d..39480ff42a5 100644
--- a/dom/media/MediaStreamGraph.cpp
+++ b/dom/media/MediaStreamGraph.cpp
@@ -3100,10 +3100,7 @@ SourceMediaStream*
 MediaStreamGraph::CreateSourceStream(DOMMediaStream* aWrapper)
 {
   SourceMediaStream* stream = new SourceMediaStream(aWrapper);
-  NS_ADDREF(stream);
-  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
-  stream->SetGraphImpl(graph);
-  graph->AppendMessage(new CreateMessage(stream));
+  AddStream(stream);
   return stream;
 }
 
@@ -3111,10 +3108,7 @@ ProcessedMediaStream*
 MediaStreamGraph::CreateTrackUnionStream(DOMMediaStream* aWrapper)
 {
   TrackUnionStream* stream = new TrackUnionStream(aWrapper);
-  NS_ADDREF(stream);
-  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
-  stream->SetGraphImpl(graph);
-  graph->AppendMessage(new CreateMessage(stream));
+  AddStream(stream);
   return stream;
 }
 
@@ -3122,10 +3116,7 @@ ProcessedMediaStream*
 MediaStreamGraph::CreateAudioCaptureStream(DOMMediaStream* aWrapper)
 {
   AudioCaptureStream* stream = new AudioCaptureStream(aWrapper);
-  NS_ADDREF(stream);
-  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
-  stream->SetGraphImpl(graph);
-  graph->AppendMessage(new CreateMessage(stream));
+  AddStream(stream);
   return stream;
 }
 
@@ -3137,10 +3128,7 @@ MediaStreamGraph::CreateAudioNodeExternalInputStream(AudioNodeEngine* aEngine)
 
   AudioNodeExternalInputStream* stream = new AudioNodeExternalInputStream(
     aEngine, GraphRate(), aEngine->NodeMainThread()->Context()->Id());
-  NS_ADDREF(stream);
-  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
-  stream->SetGraphImpl(graph);
-  graph->AppendMessage(new CreateMessage(stream));
+  AddStream(stream);
   return stream;
 }
 
@@ -3158,18 +3146,24 @@ MediaStreamGraph::CreateAudioNodeStream(AudioNodeEngine* aEngine,
                                                                 NO_AUDIO_CONTEXT;
   AudioNodeStream* stream = new AudioNodeStream(aEngine, aKind, GraphRate(),
                                                 contextIdForStream);
-  NS_ADDREF(stream);
-  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
-  stream->SetGraphImpl(graph);
   if (aEngine->HasNode()) {
     stream->SetChannelMixingParametersImpl(aEngine->NodeMainThread()->ChannelCount(),
                                            aEngine->NodeMainThread()->ChannelCountModeValue(),
                                            aEngine->NodeMainThread()->ChannelInterpretationValue());
   }
-  graph->AppendMessage(new CreateMessage(stream));
+  AddStream(stream);
   return stream;
 }
 
+void
+MediaStreamGraph::AddStream(MediaStream* aStream)
+{
+  NS_ADDREF(aStream);
+  MediaStreamGraphImpl* graph = static_cast<MediaStreamGraphImpl*>(this);
+  aStream->SetGraphImpl(graph);
+  graph->AppendMessage(new CreateMessage(aStream));
+}
+
 class GraphStartedRunnable final : public nsRunnable
 {
 public:
diff --git a/dom/media/MediaStreamGraph.h b/dom/media/MediaStreamGraph.h
index e851b613270..30c99ebef8f 100644
--- a/dom/media/MediaStreamGraph.h
+++ b/dom/media/MediaStreamGraph.h
@@ -1253,6 +1253,10 @@ public:
 
   AudioNodeExternalInputStream*
   CreateAudioNodeExternalInputStream(AudioNodeEngine* aEngine);
+  /**
+   * Add a new stream to the graph.  Main thread.
+   */
+  void AddStream(MediaStream* aStream);
 
   /* From the main thread, ask the MSG to send back an event when the graph
    * thread is running, and audio is being processed. */