--- a/dom/media/platforms/agnostic/VorbisDecoder.cpp
+++ b/dom/media/platforms/agnostic/VorbisDecoder.cpp
@@ -149,17 +149,17 @@ VorbisDataDecoder::ProcessDecode(MediaRa
 MediaResult
 VorbisDataDecoder::DoDecode(MediaRawData* aSample)
 {
   MOZ_ASSERT(mTaskQueue->IsCurrentThreadIn());
 
   const unsigned char* aData = aSample->Data();
   size_t aLength = aSample->Size();
   int64_t aOffset = aSample->mOffset;
-  uint64_t aTstampUsecs = aSample->mTime;
+  int64_t aTstampUsecs = aSample->mTime;
   int64_t aTotalFrames = 0;
 
   MOZ_ASSERT(mPacketCount >= 3);
 
   if (!mLastFrameTime || mLastFrameTime.ref() != aSample->mTime) {
     // We are starting a new block.
     mFrames = 0;
     mLastFrameTime = Some(aSample->mTime);