diff --git a/configure b/configure
index 007ae0fc6e0..4bd474084d8 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 1.332 .
+# From configure.in Revision: 1.333 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.53.
 #
@@ -1225,12 +1225,6 @@ 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 3e2143b23ab..208dc056ee7 100644
--- a/configure.in
+++ b/configure.in
@@ -20,8 +20,6 @@ VERSION=2.3
 AC_SUBST(SOVERSION)
 SOVERSION=1.0
 
-AC_DEFINE(_XOPEN_SOURCE, 500, [Needed on Tru64 and does no harm on Linux])
-
 # Arguments passed to configure.
 AC_SUBST(CONFIG_ARGS)
 CONFIG_ARGS="$ac_configure_args"
diff --git a/pyconfig.h.in b/pyconfig.h.in
index 4bfdc30f6e8..8b149324322 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -773,9 +773,6 @@
 /* Define to force use of thread-safe errno, h_errno, and other functions */
 #undef _REENTRANT
 
-/* Needed on Tru64 and does no harm on Linux */
-#undef _XOPEN_SOURCE
-
 /* Define to 1 if type `char' is unsigned and you are not using gcc.  */
 #ifndef __CHAR_UNSIGNED__
 # undef __CHAR_UNSIGNED__