diff --git a/src/xpra/client/gtk_base/gtk_client_window_base.py b/src/xpra/client/gtk_base/gtk_client_window_base.py
index f6736a7fb5..54d9a2dd30 100644
--- a/src/xpra/client/gtk_base/gtk_client_window_base.py
+++ b/src/xpra/client/gtk_base/gtk_client_window_base.py
@@ -289,6 +289,10 @@ def tell_server():
                     self.process_map_event()
         self.after_window_state_updated()
         #if we have state updates, send them back to the server using a configure window packet:
+        if self.is_OR() and not self._client.window_configure_skip_geometry:
+            #we can't do it: the server can't handle configure packets for OR windows!
+            log("not sending updated window state %s to a server which is missing the configure skip-geometry feature", self._window_state)
+            return
         def send_updated_window_state():
             if self._window_state:
                 self.process_configure_event(True)
@@ -630,6 +634,7 @@ def do_configure_event(self, event):
             self.process_configure_event()
 
     def process_configure_event(self, skip_geometry=False):
+        assert skip_geometry or not self.is_OR()
         x, y, w, h = self.get_window_geometry()
         w = max(1, w)
         h = max(1, h)
diff --git a/src/xpra/client/ui_client_base.py b/src/xpra/client/ui_client_base.py
index c73839438c..e57d79c315 100644
--- a/src/xpra/client/ui_client_base.py
+++ b/src/xpra/client/ui_client_base.py
@@ -1249,6 +1249,7 @@ def parse_server_capabilities(self):
             self.session_name = c.strget("session_name", "")
         set_application_name(self.session_name or "Xpra")
         self.window_unmap = c.boolget("window_unmap")
+        self.window_configure_skip_geometry = c.boolget("window.configure.skip-geometry")
         self.force_ungrab = c.boolget("force_ungrab")
         self.window_refresh_config = c.boolget("window_refresh_config")
         self.suspend_resume = c.boolget("suspend-resume")
diff --git a/src/xpra/x11/server.py b/src/xpra/x11/server.py
index 269435b439..ae20716f5f 100644
--- a/src/xpra/x11/server.py
+++ b/src/xpra/x11/server.py
@@ -247,6 +247,7 @@ def make_hello(self, source):
         if source.wants_features:
             capabilities["window.raise"] = True
             capabilities["window.resize-counter"] = True
+            capabilities["window.configure.skip-geometry"] = True
             capabilities["pointer.grabs"] = True
         return capabilities
 
@@ -764,7 +765,7 @@ def _process_configure_window(self, proto, packet):
                 traylog("tray %s configured to: %s", window, (x, y, w, h))
                 self._tray.move_resize(window, x, y, w, h)
         else:
-            assert not window.is_OR(), "received a configure packet for OR window %s from %s: %s" % (window, proto, packet)
+            assert not window.is_OR() or skip_geometry, "received a configure packet with geometry for OR window %s from %s: %s" % (window, proto, packet)
             self.last_client_configure_event = time.time()
             if len(packet)>=9:
                 self._set_window_state(proto, wid, window, packet[8])