--- tools/Rules.in.orig	2004-08-19 11:15:36.000000000 +0200
+++ tools/Rules.in	2008-02-11 17:07:01.000000000 +0100
@@ -19,7 +19,7 @@
 all-dirs:=$(static-dirs) $(dynamic-dirs) $(client-dirs) $(doc-dirs)
 clean-dirs:=$(all-dirs) proto sysdep
 
-CPPFLAGS=-I$(root-rel) -I$(srcdir) @CPPFLAGS@
+CPPFLAGS=-D_XOPEN_SOURCE=600 -I$(root-rel) -I$(srcdir) @CPPFLAGS@ 
 CFLAGS=$(CPPFLAGS) @CFLAGS@
 LDFLAGS=@LDFLAGS@
 LIBS=@LIBS@