Index: dat/common/dat_strerror.c
===================================================================
--- dat/common/dat_strerror.c.orig	2011-08-19 19:09:23.000000000 +0200
+++ dat/common/dat_strerror.c	2012-06-28 18:01:00.330122282 +0200
@@ -37,6 +37,10 @@
  * $Id: dat_strerror.c,v 1.10 2005/03/24 05:58:28 jlentini Exp $
  **********************************************************************/
 
+#ifdef __GNUC__
+#include <stddef.h> /* to get NULL defined */
+#endif
+
 #ifdef __KDAPL__
 #include <dat2/kdat.h>
 #else /*__UDAPL__*/