diff -Naur wmmon.app.orig/wmgeneral/wmgeneral.h wmmon.app/wmgeneral/wmgeneral.h
--- wmmon.app.orig/wmgeneral/wmgeneral.h	1999-06-07 03:09:36.000000000 +0200
+++ wmmon.app/wmgeneral/wmgeneral.h	2020-03-08 12:20:10.345121264 +0100
@@ -36,7 +36,7 @@
  /* Global variable */
 /*******************/
 
-Display		*display;
+extern Display		*display;
 
   /***********************/
  /* Function Prototypes */
diff -Naur wmmon.app.orig/wmmon/wmmon.c wmmon.app/wmmon/wmmon.c
--- wmmon.app.orig/wmmon/wmmon.c	1999-06-07 05:49:45.000000000 +0200
+++ wmmon.app/wmmon/wmmon.c	2020-03-08 12:20:18.657124944 +0100
@@ -19,6 +19,8 @@
 int	wmmon_mask_width = 64;
 int	wmmon_mask_height = 64;
 
+Display		*display;
+
 void usage(void);
 void drawstat(int *, int, int, int, int);
 void wmmon_routine(int, char **);