--- devilspie-0.22.old/src/xutils.c
+++ devilspie-0.22/src/xutils.c
@@ -305,9 +305,13 @@
   case WNCK_WINDOW_DIALOG:
     atom = my_wnck_atom_get ("_NET_WM_WINDOW_TYPE_DIALOG");
     break;
+
+#ifdef WNCK_WINDOW_MODAL_DIALOG
   case WNCK_WINDOW_MODAL_DIALOG:
     atom = my_wnck_atom_get ("_NET_WM_WINDOW_TYPE_MODAL_DIALOG");
     break;
+#endif
+
   case WNCK_WINDOW_TOOLBAR:
     atom = my_wnck_atom_get ("_NET_WM_WINDOW_TYPE_TOOLBAR");
     break;