diff --git a/ChangeLog b/ChangeLog
index a1d6901b..1d057631 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2008-09-16  Marcus Brinkmann  <marcus@g10code.com>
+
+	* configure.ac (_XOPEN_SOURCE) [apple-darwin]: Define it. 
+
 2008-07-04  Werner Koch  <wk@g10code.com>
 
 	* config.guess, config.sub: Update to 2007-11-19.  Also update
diff --git a/configure.ac b/configure.ac
index e824b475..0d2c71a7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -110,6 +110,11 @@ case "${host}" in
     *-*-gnu*)
 	have_ld_version_script=yes
         ;;
+    *-apple-darwin*)
+        AC_DEFINE(_XOPEN_SOURCE, 500, Activate POSIX interface on MacOS X)
+        ;;
+esac
+
 esac
 AM_CONDITIONAL(HAVE_LD_VERSION_SCRIPT, test "$have_ld_version_script" = "yes")