diff --git a/dom/media/MediaDecoder.cpp b/dom/media/MediaDecoder.cpp
index 9fca81fa8cb2..4990dff3c4f9 100644
--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -290,10 +290,7 @@ void MediaDecoder::Pause()
 void MediaDecoder::SetVolume(double aVolume)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  mInitialVolume = aVolume;
-  if (mDecoderStateMachine) {
-    mDecoderStateMachine->SetVolume(aVolume);
-  }
+  mVolume = aVolume;
 }
 
 void MediaDecoder::ConnectDecodedStreamToOutputStream(OutputStreamData* aStream)
@@ -602,7 +599,7 @@ MediaDecoder::MediaDecoder() :
   mDecoderPosition(0),
   mPlaybackPosition(0),
   mCurrentTime(0.0),
-  mInitialVolume(0.0),
+  mVolume(AbstractThread::MainThread(), 0.0, "MediaDecoder::mVolume (Canonical)"),
   mInitialPlaybackRate(1.0),
   mInitialPreservesPitch(true),
   mDuration(-1),
@@ -750,7 +747,6 @@ void MediaDecoder::SetStateMachineParameters()
 {
   ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
   mDecoderStateMachine->SetDuration(mDuration);
-  mDecoderStateMachine->SetVolume(mInitialVolume);
   if (GetDecodedStream()) {
     mDecoderStateMachine->SetAudioCaptured();
   }
diff --git a/dom/media/MediaDecoder.h b/dom/media/MediaDecoder.h
index 9dc3bb8c40b9..6b1940760918 100644
--- a/dom/media/MediaDecoder.h
+++ b/dom/media/MediaDecoder.h
@@ -1079,9 +1079,11 @@ protected:
   // It is read and written from the main thread only.
   double mCurrentTime;
 
-  // Volume that playback should start at.  0.0 = muted. 1.0 = full
-  // volume.  Readable/Writeable from the main thread.
-  double mInitialVolume;
+  // Volume of playback.  0.0 = muted. 1.0 = full volume.
+  Canonical<double> mVolume;
+public:
+  AbstractCanonical<double>* CanonicalVolume() { return &mVolume; }
+protected:
 
   // PlaybackRate and pitch preservation status we should start at.
   // Readable/Writeable from the main thread.
diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index 0b53d16d29e6..b6bf1a16f1b4 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -226,7 +226,7 @@ MediaDecoderStateMachine::MediaDecoderStateMachine(MediaDecoder* aDecoder,
   mDecodedAudioEndTime(-1),
   mVideoFrameEndTime(-1),
   mDecodedVideoEndTime(-1),
-  mVolume(1.0),
+  mVolume(mTaskQueue, 1.0, "MediaDecoderStateMachine::mVolume (Mirror)"),
   mPlaybackRate(1.0),
   mPreservesPitch(true),
   mLowAudioThresholdUsecs(detail::LOW_AUDIO_USECS),
@@ -307,10 +307,13 @@ MediaDecoderStateMachine::InitializationTask()
   // Connect mirrors.
   mPlayState.Connect(mDecoder->CanonicalPlayState());
   mNextPlayState.Connect(mDecoder->CanonicalNextPlayState());
+  mVolume.Connect(mDecoder->CanonicalVolume());
 
   // Initialize watchers.
   mWatchManager.Watch(mState, &MediaDecoderStateMachine::UpdateNextFrameStatus);
   mWatchManager.Watch(mAudioCompleted, &MediaDecoderStateMachine::UpdateNextFrameStatus);
+  mWatchManager.Watch(mVolume, &MediaDecoderStateMachine::VolumeChanged);
+
 }
 
 bool MediaDecoderStateMachine::HasFutureAudio() {
@@ -1355,11 +1358,10 @@ void MediaDecoderStateMachine::SetState(State aState)
   mSentPlaybackEndedEvent = false;
 }
 
-void MediaDecoderStateMachine::SetVolume(double volume)
+void MediaDecoderStateMachine::VolumeChanged()
 {
-  NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
+  MOZ_ASSERT(OnTaskQueue());
   ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
-  mVolume = volume;
   if (mAudioSink) {
     mAudioSink->SetVolume(mVolume);
   }
@@ -2545,6 +2547,7 @@ MediaDecoderStateMachine::FinishShutdown()
   // Disconnect canonicals and mirrors before shutting down our task queue.
   mPlayState.DisconnectIfConnected();
   mNextPlayState.DisconnectIfConnected();
+  mVolume.DisconnectIfConnected();
   mNextFrameStatus.DisconnectAll();
 
   // Shut down the watch manager before shutting down our task queue.
diff --git a/dom/media/MediaDecoderStateMachine.h b/dom/media/MediaDecoderStateMachine.h
index 9b67e779e9fb..770b8f0e71db 100644
--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -152,9 +152,6 @@ public:
     return mState;
   }
 
-  // Set the audio volume. The decoder monitor must be obtained before
-  // calling this.
-  void SetVolume(double aVolume);
   void SetAudioCaptured();
 
   // Check if the decoder needs to become dormant state.
@@ -447,6 +444,7 @@ protected:
   already_AddRefed<AudioData> PopAudio();
   already_AddRefed<VideoData> PopVideo();
 
+  void VolumeChanged();
 
   class WakeDecoderRunnable : public nsRunnable {
   public:
@@ -1009,10 +1007,8 @@ protected:
   // on decoded video data.
   int64_t mDecodedVideoEndTime;
 
-  // Volume of playback. 0.0 = muted. 1.0 = full volume. Read/Written
-  // from the state machine and main threads. Synchronised via decoder
-  // monitor.
-  double mVolume;
+  // Volume of playback. 0.0 = muted. 1.0 = full volume.
+  Mirror<double> mVolume;
 
   // Playback rate. 1.0 : normal speed, 0.5 : two times slower. Synchronized via
   // decoder monitor.