--- a/dom/media/mediasource/MediaSourceDecoder.cpp
+++ b/dom/media/mediasource/MediaSourceDecoder.cpp
@@ -263,17 +263,17 @@ MediaSourceDecoder::NextFrameBufferedSta
   }
 
   // Next frame hasn't been decoded yet.
   // Use the buffered range to consider if we have the next frame available.
   TimeUnit currentPosition = TimeUnit::FromMicroseconds(CurrentPosition());
   TimeInterval interval(currentPosition,
                         currentPosition + media::TimeUnit::FromMicroseconds(DEFAULT_NEXT_FRAME_AVAILABLE_BUFFERED),
                         MediaSourceDemuxer::EOS_FUZZ);
-  return GetBuffered().Contains(interval)
+  return GetBuffered().Contains(ClampIntervalToEnd(interval))
     ? MediaDecoderOwner::NEXT_FRAME_AVAILABLE
     : MediaDecoderOwner::NEXT_FRAME_UNAVAILABLE;
 }
 
 bool
 MediaSourceDecoder::CanPlayThrough()
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -296,15 +296,25 @@ MediaSourceDecoder::CanPlayThrough()
   }
   // If we have data up to the mediasource's duration or 30s ahead, we can
   // assume that we can play without interruption.
   TimeUnit timeAhead =
     std::min(duration, currentPosition + TimeUnit::FromSeconds(30));
   TimeInterval interval(currentPosition,
                         timeAhead,
                         MediaSourceDemuxer::EOS_FUZZ);
-  return GetBuffered().Contains(interval);
+  return GetBuffered().Contains(ClampIntervalToEnd(interval));
+}
+
+TimeInterval
+MediaSourceDecoder::ClampIntervalToEnd(const TimeInterval& aInterval)
+{
+  if (!mEnded) {
+    return aInterval;
+  }
+  TimeInterval interval(TimeUnit(), TimeUnit::FromSeconds(GetDuration()));
+  return aInterval.Intersection(interval);
 }
 
 #undef MSE_DEBUG
 #undef MSE_DEBUGV
 
 } // namespace mozilla

--- a/dom/media/mediasource/MediaSourceDecoder.h
+++ b/dom/media/mediasource/MediaSourceDecoder.h
@@ -78,16 +78,17 @@ public:
 
   void AddSizeOfResources(ResourceSizes* aSizes) override;
 
   MediaDecoderOwner::NextFrameStatus NextFrameBufferedStatus() override;
   bool CanPlayThrough() override;
 
 private:
   void DoSetMediaSourceDuration(double aDuration);
+  media::TimeInterval ClampIntervalToEnd(const media::TimeInterval& aInterval);
 
   // The owning MediaSource holds a strong reference to this decoder, and
   // calls Attach/DetachMediaSource on this decoder to set and clear
   // mMediaSource.
   dom::MediaSource* mMediaSource;
   RefPtr<MediaSourceDemuxer> mDemuxer;
   RefPtr<MediaFormatReader> mReader;