diff -up a/vncviewer/CConn.cxx.newfbsize b/vncviewer/CConn.cxx
--- a/vncviewer/CConn.cxx.newfbsize	2008-10-23 13:00:59.000000000 +0200
+++ b/vncviewer/CConn.cxx	2008-10-23 13:01:11.000000000 +0200
@@ -327,6 +327,8 @@ void CConn::beginRect(const Rect& r, uns
   if (encoding != encodingCopyRect) {
     lastServerEncoding = encoding;
   }
+  if (encoding == pseudoEncodingDesktopSize)
+    setDesktopSize( r.width(), r.height() );
 }
 
 void CConn::endRect(const Rect& r, int encoding)