diff --git a/common/rfb/VNCServerST.cxx b/common/rfb/VNCServerST.cxx
index 6d21c7b..06921e7 100644
--- a/common/rfb/VNCServerST.cxx
+++ b/common/rfb/VNCServerST.cxx
@@ -484,8 +484,10 @@
 
   pb->grabRegion(toCheck);
 
-  if (rfb::Server::compareFB)
+  if (rfb::Server::compareFB) {
     comparer->compare();
+    comparer->getUpdateInfo(&ui, pb->getRect());
+  }
 
   if (renderCursor) {
     pb->getImage(renderedCursor.data,