diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
index 8fd573b..f238480 100644
--- a/LayoutTests/ChangeLog
+++ b/LayoutTests/ChangeLog
@@ -1,3 +1,13 @@
+2019-11-25  youenn fablet  <youenn@apple.com>
+
+        Mark imported/w3c/web-platform-tests/webrtc/RTCRtpReceiver-getSynchronizationSources.https.html as Slow
+        https://bugs.webkit.org/show_bug.cgi?id=204567
+
+        Unreviewed.
+
+        * TestExpectations:
+        Mark above test as slow as it takes at least 20 seconds to run.
+
 2019-11-24  Jonathan Bedard  <jbedard@apple.com>
 
         [WebGL] Garden dedicated queue (Part 4)
diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
index 7809de4..96efc41 100644
--- a/LayoutTests/TestExpectations
+++ b/LayoutTests/TestExpectations
@@ -1790,6 +1790,7 @@
 
 webrtc/simulcast-h264.html [ Slow ]
 webrtc/datachannel/multiple-connections.html [ Slow ]
+imported/w3c/web-platform-tests/webrtc/RTCRtpReceiver-getSynchronizationSources.https.html [ Slow ]
 webkit.org/b/171094 imported/w3c/web-platform-tests/webrtc/rtcpeerconnection/rtcpeerconnection-idl.html [ Failure DumpJSConsoleLogInStdErr ]
 webkit.org/b/172f21 imported/w3c/web-platform-tests/webrtc/getstats.html [ Failure ]
 imported/w3c/web-platform-tests/webrtc/RTCPeerConnection-setLocalDescription-offer.html [ Failure ]