diff -urN ../nagios.orig/include/config.h.in ./include/config.h.in
--- ../nagios.orig/include/config.h.in	2005-01-11 10:13:09.000000000 +0100
+++ ./include/config.h.in	2005-05-02 13:49:31.000000000 +0200
@@ -19,6 +19,11 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  ************************************************************************/
 
+#ifdef NSCORE
+# define _REENTRANT
+# define _THREAD_SAFE
+#endif
+
 #include <stdio.h>
 #include <stdlib.h>
 
