diff --git a/openbox/screen.c b/openbox/screen.c
index 2556b94c..d37288fa 100644
--- a/openbox/screen.c
+++ b/openbox/screen.c
@@ -201,7 +201,7 @@ gboolean screen_annex()
                window, screen_support_win);
 
     /* set the _NET_SUPPORTED_ATOMS hint */
-    num_support = 50;
+    num_support = 51;
     i = 0;
     supported = g_new(guint32, num_support);
     supported[i++] = prop_atoms.net_current_desktop;
@@ -254,6 +254,7 @@ gboolean screen_annex()
     supported[i++] = prop_atoms.net_wm_state_below;
     supported[i++] = prop_atoms.net_moveresize_window;
     supported[i++] = prop_atoms.net_wm_moveresize;
+    supported[i++] = prop_atoms.ob_wm_state_undecorated;
     g_assert(i == num_support);
 /*
   supported[] = prop_atoms.net_wm_action_stick;