--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -3047,16 +3047,22 @@ void MediaDecoderStateMachine::BufferedR
   }
 
   bool exists;
   media::TimeUnit end{ mBuffered.Ref().GetEnd(&exists) };
   if (!exists) {
     return;
   }
 
+  // We need to check mInfo.isSome() because that this method might be invoked
+  // before the metadata been read.
+  if (mInfo.isNothing() || Info().mMetadataDuration.isNothing()) {
+    return;
+  }
+
   // Use estimated duration from buffer ranges when mDuration is unknown or
   // the estimated duration is larger.
   if (mDuration.Ref().isNothing() || mDuration.Ref()->IsInfinite() ||
       end > mDuration.Ref().ref()) {
     mDuration = Some(end);
   }
 }