diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index 245be46b4de2..b1390ece876a 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2805,6 +2805,11 @@ bool MediaDecoderStateMachine::IsPlaying() const
   return mMediaSink->IsPlaying();
 }
 
+void MediaDecoderStateMachine::SetMediaNotSeekable()
+{
+  mMediaSeekable = false;
+}
+
 nsresult MediaDecoderStateMachine::Init(MediaDecoder* aDecoder)
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -2821,11 +2826,8 @@ nsresult MediaDecoderStateMachine::Init(MediaDecoder* aDecoder)
 
   mMetadataManager.Connect(mReader->TimedMetadataEvent(), OwnerThread());
 
-  RefPtr<MediaDecoderStateMachine> self = this;
   mOnMediaNotSeekable = mReader->OnMediaNotSeekable().Connect(
-    OwnerThread(), [self] () {
-      self->mMediaSeekable = false;
-    });
+    OwnerThread(), this, &MediaDecoderStateMachine::SetMediaNotSeekable);
 
   mMediaSink = CreateMediaSink(mAudioCaptured);
 
@@ -2838,6 +2840,7 @@ nsresult MediaDecoderStateMachine::Init(MediaDecoder* aDecoder)
   nsresult rv = mReader->Init();
   NS_ENSURE_SUCCESS(rv, rv);
 
+  RefPtr<MediaDecoderStateMachine> self = this;
   OwnerThread()->Dispatch(NS_NewRunnableFunction([self] () {
     MOZ_ASSERT(!self->mStateObj);
     auto s = new DecodeMetadataState(self);
diff --git a/dom/media/MediaDecoderStateMachine.h b/dom/media/MediaDecoderStateMachine.h
index 46b4d2a1af14..57abc3a2b62a 100644
--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -297,6 +297,9 @@ private:
   // be held.
   bool IsPlaying() const;
 
+  // Sets mMediaSeekable to false.
+  void SetMediaNotSeekable();
+
   // Resets all states related to decoding and aborts all pending requests
   // to the decoders.
   void ResetDecode(TrackSet aTracks = TrackSet(TrackInfo::kAudioTrack,