--- a/dom/media/webrtc/MediaEngineRemoteVideoSource.cpp
+++ b/dom/media/webrtc/MediaEngineRemoteVideoSource.cpp
@@ -351,16 +351,23 @@ MediaEngineRemoteVideoSource::FrameSizeC
 #if defined(MOZ_WIDGET_GONK)
   mMonitor.AssertCurrentThreadOwns(); // mWidth and mHeight are protected...
 #endif
   if ((mWidth < 0) || (mHeight < 0) ||
       (w !=  (unsigned int) mWidth) || (h != (unsigned int) mHeight)) {
     LOG(("MediaEngineRemoteVideoSource Video FrameSizeChange: %ux%u was %ux%u", w, h, mWidth, mHeight));
     mWidth = w;
     mHeight = h;
+
+    RefPtr<MediaEngineRemoteVideoSource> that = this;
+    NS_DispatchToMainThread(media::NewRunnableFrom([that, w, h]() mutable {
+      that->mSettings.mWidth.Value() = w;
+      that->mSettings.mHeight.Value() = h;
+      return NS_OK;
+    }));
   }
 }
 
 int
 MediaEngineRemoteVideoSource::DeliverFrame(uint8_t* aBuffer ,
                                     const camera::VideoFrameProperties& aProps)
 {
   // Check for proper state.