--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2991,17 +2991,17 @@ void MediaDecoderStateMachine::Recompute
   // The duration is always exactly known with MSE and there's no need to adjust
   // it based on what may have been seen in the past; in particular as this data
   // may no longer exist such as when the mediasource duration was reduced.
   if (mExplicitDuration.Ref().isNothing()
       && duration < mObservedDuration.Ref()) {
     duration = mObservedDuration;
   }
 
-  MOZ_ASSERT(duration.ToMicroseconds() >= 0);
+  MOZ_ASSERT(duration >= TimeUnit::Zero());
   mDuration = Some(duration);
 }
 
 RefPtr<ShutdownPromise>
 MediaDecoderStateMachine::Shutdown()
 {
   MOZ_ASSERT(OnTaskQueue());
   return mStateObj->HandleShutdown();