Index: data.c
===================================================================
--- data.c	(revision 29728)
+++ data.c	(revision 29729)
@@ -4,6 +4,7 @@
  *  pcb-rnd, interactive printed circuit board design
  *  (this file is based on PCB, interactive printed circuit board design)
  *  Copyright (C) 1994,1995,1996 Thomas Nau
+ *  Copyright (C) 2020 Tibor 'Igor2' Palinkas
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -43,6 +44,7 @@
 #include "operation.h"
 #include "flag.h"
 #include "undo_old.h"
+#include "undo.h"
 #include "obj_arc.h"
 #include "obj_line.h"
 #include "obj_poly.h"