diff --git a/common/rfb/ComparingUpdateTracker.cxx b/common/rfb/ComparingUpdateTracker.cxx
index 8d4311a..1d27f3c 100644
--- a/common/rfb/ComparingUpdateTracker.cxx
+++ b/common/rfb/ComparingUpdateTracker.cxx
@@ -157,6 +157,8 @@
     oldData += oldStrideBytes * BLOCK_SIZE;
   }
 
+  oldFb.commitBufferRW(r);
+
   if (!changedBlocks.empty()) {
     Region temp;
     temp.setOrderedRects(changedBlocks);