--- src/blackbox.hh	2002-06-20 22:00:27.000000000 +0200
+++ src/blackbox.hh	2004-06-16 17:09:53.924919320 +0200
@@ -27,6 +27,7 @@
 extern "C" {
 #include <X11/Xlib.h>
 #include <X11/Xresource.h>
+#include <assert.h>
 
 #ifdef    HAVE_STDIO_H
 # include <stdio.h>