diff --git a/src/xpra/x11/desktop_server.py b/src/xpra/x11/desktop_server.py
index a3beb7d434..de5caf0fb5 100644
--- a/src/xpra/x11/desktop_server.py
+++ b/src/xpra/x11/desktop_server.py
@@ -507,7 +507,7 @@ def _process_unmap_window(self, proto, packet):
 
     def _process_configure_window(self, proto, packet):
         wid, x, y, w, h = packet[1:6]
-        if len(packet)>=13:
+        if len(packet)>=13 and not self.readonly:
             pwid = packet[10]
             pointer = packet[11]
             modifiers = packet[12]