--- a/dom/media/mediasource/MediaSourceDecoder.cpp
+++ b/dom/media/mediasource/MediaSourceDecoder.cpp
@@ -80,17 +80,18 @@ MediaSourceDecoder::GetSeekable()
 
   media::TimeIntervals seekable;
   double duration = mMediaSource->Duration();
   if (IsNaN(duration)) {
     // Return empty range.
   } else if (duration > 0 && mozilla::IsInfinite(duration)) {
     media::TimeIntervals buffered = GetBuffered();
     if (buffered.Length()) {
-      seekable += media::TimeInterval(buffered.GetStart(), buffered.GetEnd());
+      seekable +=
+        media::TimeInterval(media::TimeUnit::FromSeconds(0), buffered.GetEnd());
     }
   } else {
     seekable += media::TimeInterval(media::TimeUnit::FromSeconds(0),
                                     media::TimeUnit::FromSeconds(duration));
   }
   MSE_DEBUG("ranges=%s", DumpTimeRanges(seekable).get());
   return seekable;
 }