--- gdk/x11/gdkproperty-x11-orig.c	2009-07-17 23:53:24.000000000 -0400
+++ gdk/x11/gdkproperty-x11.c	2009-08-13 09:56:27.000000000 -0400
@@ -160,6 +160,8 @@
 {
   GdkDisplayX11 *display_x11 = GDK_DISPLAY_X11 (display);
 
+  g_return_val_if_fail (atom != GDK_NONE, None);
+
   if (ATOM_TO_INDEX (atom) < G_N_ELEMENTS (xatoms_offset) - N_CUSTOM_PREDEFINED)
     return ATOM_TO_INDEX (atom);
   
@@ -230,7 +231,7 @@
   for (i = 0; i < n_atoms; i++)
     {
       GdkAtom atom = gdk_atom_intern_static_string (atom_names[i]);
-      if (lookup_cached_xatom (display, atom) == None)
+      if (atom != GDK_NONE && lookup_cached_xatom (display, atom) == None)
 	{
 	  atoms[n_xatoms] = atom;
 	  xatom_names[n_xatoms] = atom_names[i];