Index: trunk/src/route.c
===================================================================
--- trunk/src/route.c	(revision 19348)
+++ trunk/src/route.c	(revision 19349)
@@ -548,7 +548,7 @@
 					}
 
 					if(p_route->thickness != apply_to_arc->Thickness) {
-						pcb_undo_add_obj_to_size(PCB_OBJ_ARC, Layer, Arc, Arc);
+						pcb_undo_add_obj_to_size(PCB_OBJ_ARC, apply_to_arc_layer, apply_to_arc, apply_to_arc);
 						++changes;
 					}