Index: obj_pstk_proto.c
===================================================================
--- obj_pstk_proto.c	(revision 31561)
+++ obj_pstk_proto.c	(revision 31562)
@@ -1395,7 +1395,12 @@
 	pcb_pstk_tshape_t *tshp = &proto->tr.array[tridx];
 	pcb_pstk_shape_t *shp = &tshp->shape[shpidx];
 
-	TODO("padstack: undo")
+	if (undoable) {
+		undo_shape_geo_t *g = pstk_shape_geo_undo_init(proto, tridx, shpidx);
+		pcb_pstk_shape_copy(&g->shp, shp);
+		g->shp_valid = 1;
+		pcb_undo_inc_serial();
+	}
 
 	pcb_pstk_shape_scale_(shp, sx, sy);
 }