diff --git a/src/gui_athena.c b/src/gui_athena.c
index 6cbabf8..8b5af63 100644
--- a/src/gui_athena.c
+++ b/src/gui_athena.c
@@ -1191,7 +1191,7 @@
 #endif
 
 	menu->parent = parent;
-	menu->submenu_id = NULL;
+	menu->submenu_id = (Widget)0;
 	if (!XtIsManaged(toolBar)
 		    && vim_strchr(p_go, GO_TOOLBAR) != NULL)
 	    gui_mch_show_toolbar(TRUE);