diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index 8871ffcf1e..9d6aa124eb 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -1906,12 +1906,24 @@ MediaDecoderStateMachine::InitiateSeek()
   Reset();
 
   // Do the seek.
+  nsRefPtr<MediaDecoderStateMachine> self = this;
   mSeekRequest.Begin(ProxyMediaCall(DecodeTaskQueue(), mReader.get(), __func__,
                                     &MediaDecoderReader::Seek, mCurrentSeek.mTarget.mTime,
                                     GetEndTime())
-    ->RefableThen(TaskQueue(), __func__, this,
-                  &MediaDecoderStateMachine::OnSeekCompleted,
-                  &MediaDecoderStateMachine::OnSeekFailed));
+    ->RefableThen(TaskQueue(), __func__,
+                  [self] (int64_t) -> void {
+                    ReentrantMonitorAutoEnter mon(self->mDecoder->GetReentrantMonitor());
+                    self->mSeekRequest.Complete();
+                    // We must decode the first samples of active streams, so we can determine
+                    // the new stream time. So dispatch tasks to do that.
+                    self->mDecodeToSeekTarget = true;
+                    self->DispatchDecodeTasksIfNeeded();
+                  }, [self] (nsresult aResult) -> void {
+                    ReentrantMonitorAutoEnter mon(self->mDecoder->GetReentrantMonitor());
+                    self->mSeekRequest.Complete();
+                    MOZ_ASSERT(NS_FAILED(aResult), "Cancels should also disconnect mSeekRequest");
+                    self->DecodeError();
+                  }));
 }
 
 nsresult
@@ -2399,30 +2411,6 @@ MediaDecoderStateMachine::FinishDecodeFirstFrame()
   return NS_OK;
 }
 
-void
-MediaDecoderStateMachine::OnSeekCompleted(int64_t aTime)
-{
-  MOZ_ASSERT(OnTaskQueue());
-  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
-  mSeekRequest.Complete();
-
-  // We must decode the first samples of active streams, so we can determine
-  // the new stream time. So dispatch tasks to do that.
-  mDecodeToSeekTarget = true;
-
-  DispatchDecodeTasksIfNeeded();
-}
-
-void
-MediaDecoderStateMachine::OnSeekFailed(nsresult aResult)
-{
-  MOZ_ASSERT(OnTaskQueue());
-  ReentrantMonitorAutoEnter mon(mDecoder->GetReentrantMonitor());
-  mSeekRequest.Complete();
-  MOZ_ASSERT(NS_FAILED(aResult), "Cancels should also disconnect mSeekRequest");
-  DecodeError();
-}
-
 void
 MediaDecoderStateMachine::SeekCompleted()
 {
diff --git a/dom/media/MediaDecoderStateMachine.h b/dom/media/MediaDecoderStateMachine.h
index 28981260d4..4375812c8c 100644
--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -431,9 +431,6 @@ public:
     OnNotDecoded(MediaData::VIDEO_DATA, aReason);
   }
 
-  void OnSeekCompleted(int64_t aTime);
-  void OnSeekFailed(nsresult aResult);
-
   // Resets all state related to decoding and playback, emptying all buffers
   // and aborting all pending operations on the decode task queue.
   void Reset();