Index: obj_arc.c
===================================================================
--- obj_arc.c	(revision 20170)
+++ obj_arc.c	(revision 20171)
@@ -71,7 +71,7 @@
 	arclist_remove(arc);
 	assert(layer->parent_type == PCB_PARENT_DATA);
 	pcb_obj_id_del(layer->parent.data, arc);
-	PCB_SET_PARENT(arc, layer, NULL);
+	PCB_CLEAR_PARENT(arc);
 }
 
 pcb_arc_t *pcb_arc_alloc(pcb_layer_t * layer)