diff --git a/test/scenario/video_frame_matcher.cc b/test/scenario/video_frame_matcher.cc
index 912459183f..d2b0ee231f 100644
--- a/test/scenario/video_frame_matcher.cc
+++ b/test/scenario/video_frame_matcher.cc
@@ -158,7 +158,9 @@ void ForwardingCapturedFrameTap::OnDiscardedFrame() {
 void ForwardingCapturedFrameTap::AddOrUpdateSink(
     VideoSinkInterface<VideoFrame>* sink,
     const rtc::VideoSinkWants& wants) {
-  sink_ = sink;
+  if (!sink_)
+    sink_ = sink;
+  RTC_DCHECK_EQ(sink_, sink);
   source_->AddOrUpdateSink(this, wants);
 }
 void ForwardingCapturedFrameTap::RemoveSink(
diff --git a/test/scenario/video_frame_matcher.h b/test/scenario/video_frame_matcher.h
index 20a0ccca8b..f7f62436ac 100644
--- a/test/scenario/video_frame_matcher.h
+++ b/test/scenario/video_frame_matcher.h
@@ -114,7 +114,7 @@ class ForwardingCapturedFrameTap
   Clock* const clock_;
   VideoFrameMatcher* const matcher_;
   rtc::VideoSourceInterface<VideoFrame>* const source_;
-  VideoSinkInterface<VideoFrame>* sink_;
+  VideoSinkInterface<VideoFrame>* sink_ = nullptr;
   int discarded_count_ = 0;
 };