diff --git a/dom/media/webm/WebMDemuxer.cpp b/dom/media/webm/WebMDemuxer.cpp
index 00b63b65b92b..f2d6be7985c5 100644
--- a/dom/media/webm/WebMDemuxer.cpp
+++ b/dom/media/webm/WebMDemuxer.cpp
@@ -692,14 +692,16 @@ WebMDemuxer::GetNextPacket(TrackInfo::TrackType aType,
         if (isKeyframe) {
           // We only look for resolution changes on keyframes for both VP8 and
           // VP9. Other resolution changes are invalid.
-          auto dimensions = nsIntSize(si.w, si.h);
-          if (mLastSeenFrameSize.isSome()
-              && (dimensions != mLastSeenFrameSize.value())) {
-            mInfo.mVideo.mDisplay = dimensions;
+          if (mLastSeenFrameWidth.isSome()
+              && mLastSeenFrameHeight.isSome()
+              && (si.w != mLastSeenFrameWidth.value()
+                  || si.h != mLastSeenFrameHeight.value())) {
+            mInfo.mVideo.mDisplay = nsIntSize(si.w, si.h);
             mSharedVideoTrackInfo =
               new TrackInfoSharedPtr(mInfo.mVideo, ++sStreamSourceID);
           }
-          mLastSeenFrameSize = Some(dimensions);
+          mLastSeenFrameWidth = Some(si.w);
+          mLastSeenFrameHeight = Some(si.h);
         }
       }
     }
diff --git a/dom/media/webm/WebMDemuxer.h b/dom/media/webm/WebMDemuxer.h
index d9f030155d3d..421052cabf8f 100644
--- a/dom/media/webm/WebMDemuxer.h
+++ b/dom/media/webm/WebMDemuxer.h
@@ -257,7 +257,8 @@ private:
   int64_t mLastWebMBlockOffset;
   const bool mIsMediaSource;
 
-  Maybe<nsIntSize> mLastSeenFrameSize;
+  Maybe<uint32_t> mLastSeenFrameWidth;
+  Maybe<uint32_t> mLastSeenFrameHeight;
   // This will be populated only if a resolution change occurs, otherwise it
   // will be left as null so the original metadata is used
   RefPtr<TrackInfoSharedPtr> mSharedVideoTrackInfo;