diff --git a/Include/Python.h b/Include/Python.h
index 32efa0ceb33..2d5e2a6e3eb 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -9,13 +9,8 @@
 # define _GNU_SOURCE	1
 #endif
 
-/* Forcing SUSv2 compatibility still produces problems on some
-   platforms, True64 and SGI IRIX being two of them, so for now the
-   define is switched off. */
-#if 0
 #ifndef _XOPEN_SOURCE
-# define _XOPEN_SOURCE	500
-#endif
+# define _XOPEN_SOURCE 500
 #endif
 
 /* Include nearly all Python header files */
diff --git a/configure b/configure
index 2696de10859..1641fd10a4e 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 1.329 .
+# From configure.in Revision: 1.330 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.53.
 #
@@ -1225,6 +1225,11 @@ VERSION=2.3
 
 SOVERSION=1.0
 
+cat >>confdefs.h <<\_ACEOF
+#define _XOPEN_SOURCE 500
+_ACEOF
+
+
 # Arguments passed to configure.
 
 CONFIG_ARGS="$ac_configure_args"
diff --git a/configure.in b/configure.in
index 69bbd7f466e..2d7b695fd62 100644
--- a/configure.in
+++ b/configure.in
@@ -20,6 +20,8 @@ VERSION=2.3
 AC_SUBST(SOVERSION)
 SOVERSION=1.0
 
+AC_DEFINE(_XOPEN_SOURCE, 500)
+
 # Arguments passed to configure.
 AC_SUBST(CONFIG_ARGS)
 CONFIG_ARGS="$ac_configure_args"