diff -up libdbusmenu-16.04.0/libdbusmenu-16.04.0/libdbusmenu-glib/menuitem.c.covscan libdbusmenu-16.04.0/libdbusmenu-16.04.0/libdbusmenu-glib/menuitem.c
--- libdbusmenu-16.04.0/libdbusmenu-16.04.0/libdbusmenu-glib/menuitem.c.covscan	2016-02-27 19:58:43.000000000 +0100
+++ libdbusmenu-16.04.0/libdbusmenu-16.04.0/libdbusmenu-glib/menuitem.c	2018-10-09 12:56:22.308956723 +0200
@@ -1753,6 +1753,7 @@ dbusmenu_menuitem_handle_event (Dbusmenu
 	g_debug("Menuitem %d (%s) is getting event '%s'", ID(mi), LABEL(mi), name);
 	#endif
 	DbusmenuMenuitemClass * class = DBUSMENU_MENUITEM_GET_CLASS(mi);
+	g_return_if_fail(DBUSMENU_IS_MENUITEM_CLASS(class));
 
 	gboolean handled = FALSE;
 	if (variant == NULL) {