--- a/dom/media/platforms/wmf/WMFDecoderModule.cpp
+++ b/dom/media/platforms/wmf/WMFDecoderModule.cpp
@@ -209,26 +209,28 @@ WMFDecoderModule::Supports(const TrackIn
   if ((aTrackInfo.mMimeType.EqualsLiteral("audio/mp4a-latm") ||
        aTrackInfo.mMimeType.EqualsLiteral("audio/mp4")) &&
        WMFDecoderModule::HasAAC()) {
     return true;
   }
   if (MP4Decoder::IsH264(aTrackInfo.mMimeType) && WMFDecoderModule::HasH264()) {
     const VideoInfo* videoInfo = aTrackInfo.GetAsVideoInfo();
     MOZ_ASSERT(videoInfo);
+    int32_t w = videoInfo->mImage.width;
+    int32_t h = videoInfo->mImage.height;
     // Check Windows format constraints, based on:
     // https://msdn.microsoft.com/en-us/library/windows/desktop/dd797815(v=vs.85).aspx
     if (IsWin8OrLater()) {
       // Windows >7 supports at most 4096x2304.
-      if (videoInfo->mImage.width > 4096 || videoInfo->mImage.height > 2304) {
+      if (w > 4096 || h > 2304) {
         return false;
       }
     } else {
       // Windows <=7 supports at most 1920x1088.
-      if (videoInfo->mImage.width > 1920 || videoInfo->mImage.height > 1088) {
+      if (w > 1920 || h > 1088) {
         return false;
       }
     }
     return true;
   }
   if (aTrackInfo.mMimeType.EqualsLiteral("audio/mpeg") &&
       CanCreateWMFDecoder<CLSID_CMP3DecMediaObject>()) {
     return true;