diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index 24941a0b248f..0c39b6c69add 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2864,11 +2864,6 @@ MediaDecoderStateMachine::ScheduleStateMachineIn(int64_t aMicroseconds)
   mDelayedScheduler.Ensure(target);
 }
 
-bool MediaDecoderStateMachine::OnDecodeTaskQueue() const
-{
-  return !DecodeTaskQueue() || DecodeTaskQueue()->IsCurrentThreadIn();
-}
-
 bool MediaDecoderStateMachine::OnTaskQueue() const
 {
   return OwnerThread()->IsCurrentThreadIn();
diff --git a/dom/media/MediaDecoderStateMachine.h b/dom/media/MediaDecoderStateMachine.h
index ceb6d11fac6d..f27d96a73be8 100644
--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -235,8 +235,6 @@ public:
 
   // Functions used by assertions to ensure we're calling things
   // on the appropriate threads.
-  bool OnDecodeTaskQueue() const;
-
   bool OnTaskQueue() const;
 
   size_t SizeOfVideoQueue() {