diff -up crystal-stacker-1.5/ce/source/externs.h~ crystal-stacker-1.5/ce/source/externs.h

--- crystal-stacker-1.5/ce/source/externs.h~	2001-03-31 07:27:24.000000000 +0200

+++ crystal-stacker-1.5/ce/source/externs.h	2020-03-03 23:05:10.357371067 +0100

@@ -27,7 +27,7 @@ extern BITMAP * toolpic;

 extern BITMAP * leftbar;

 extern BITMAP * tool[TOTAL_TOOLS];

-void (*update_proc)();

+extern void (*update_proc)();

 extern SETTINGS ThemeSettings;

diff -up crystal-stacker-1.5/ce/source/ce.c~ crystal-stacker-1.5/ce/source/ce.c

--- crystal-stacker-1.5/ce/source/ce.c~	2006-04-04 22:15:40.000000000 +0200

+++ crystal-stacker-1.5/ce/source/ce.c	2020-03-03 23:13:41.019229310 +0100

@@ -1,6 +1,8 @@

 #include "palette.h"

 #include "includes.h"

+void (*update_proc)();

+

 /* sets up the main menu */

 void make_main_menu(void)

 {