diff --git a/common/rfb/VNCSConnectionST.cxx b/common/rfb/VNCSConnectionST.cxx
index b2ceb7d..5b9152c 100644
--- a/common/rfb/VNCSConnectionST.cxx
+++ b/common/rfb/VNCSConnectionST.cxx
@@ -764,6 +764,7 @@
 
   // Stuff still waiting in the send buffer?
   sock->outStream().flush();
+  congestion.debugTrace("congestion-trace.csv", sock->getFd());
   if (sock->outStream().bufferUsage() > 0)
     return true;