--- a/unix/video.c	2020-07-05 15:45:25.681756444 +0200
+++ a/unix/video.c	2020-07-05 15:45:30.605089743 +0200
@@ -11,7 +11,7 @@
  * Copyright 1992 Ken Shirriff
  */
 
-WINDOW *curwin;
+extern WINDOW *curwin;
 
 extern unsigned char *xgetfont (void);
 extern int startdisk (void);