diff -Naur wmCalClock-1.25.orig/Src/xutils.c wmCalClock-1.25/Src/xutils.c
--- a/xutils.c	1999-03-27 07:46:38.000000000 +0100
+++ b/xutils.c	2020-01-29 18:55:05.062360592 +0100
@@ -52,6 +52,11 @@
 GC		NormalGC;
 XpmIcon		wmgen;
 Pixmap		pixmask;
+Display		*display;
+Window      Root;
+Window      iconwin, win;
+int         screen; 
+int         DisplayDepth;
 
 
 /*
diff -Naur wmCalClock-1.25.orig/Src/xutils.h wmCalClock-1.25/Src/xutils.h
--- a/xutils.h	1999-03-27 07:46:38.000000000 +0100
+++ b/xutils.h	2020-01-29 18:54:54.360359886 +0100
@@ -18,11 +18,11 @@
 /*
  *   Global variable
  */
-Display		*display;
-Window          Root;
-Window          iconwin, win;
-int             screen; 
-int             DisplayDepth;
+extern Display	*display;
+extern Window   Root;
+extern Window   iconwin, win;
+extern int      screen; 
+extern int      DisplayDepth;