Index: b/src/virt-manager.py.in
===================================================================
--- a/src/virt-manager.py.in
+++ b/src/virt-manager.py.in
@@ -271,11 +271,11 @@ def main():
     # Urgh, pygtk merely logs a warning when failing to open
     # the X11 display connection, and lets everything carry
     # on as if all were fine. Ultimately bad stuff happens,
     # so lets catch it here & get the hell out...
     import warnings
-    warnings.filterwarnings('error', module='gtk')
+    warnings.filterwarnings('error', module='gtk', append=True)
     try:
         import gobject
 
         # Set program name for gnome shell (before importing gtk, which
         # seems to call set_prgname on its own)