diff --git a/src/xpra/server_source.py b/src/xpra/server_source.py
index 9ba52e5d91..66388ce3cc 100644
--- a/src/xpra/server_source.py
+++ b/src/xpra/server_source.py
@@ -625,7 +625,7 @@ def _make_metadata(self, wid, window, propname):
             cache["tray"] = window.is_tray()
             try:
                 from wimpiggy.lowlevel import get_xwindow       #@UnresolvedImport
-                cache["xid"] = get_xwindow(window.client_window)
+                cache["xid"] = hex(get_xwindow(window.client_window))
             except:
                 pass
         props = self.do_make_metadata(window, propname)