--- a/dom/media/ogg/OggDemuxer.cpp
+++ b/dom/media/ogg/OggDemuxer.cpp
@@ -1359,16 +1359,17 @@ OggTrackDemuxer::NextSample()
   // mDecodedAudioDuration gets adjusted during ReadOggChain().
   TimeUnit totalDuration = mParent->mDecodedAudioDuration;
   if (eos) {
     // We've encountered an end of bitstream packet; check for a chained
     // bitstream following this one.
     // This will also update mSharedAudioTrackInfo.
     mParent->ReadOggChain(data->GetEndTime());
   }
+  data->mOffset = mParent->Resource(mType)->Tell();
   // We adjust the start time of the sample to account for the potential ogg chaining.
   data->mTime += totalDuration;
   return data;
 }
 
 RefPtr<OggTrackDemuxer::SamplesPromise>
 OggTrackDemuxer::GetSamples(int32_t aNumSamples)
 {