@@ -13,11 +13,13 @@
  * file.
  */
 
 #include "config.h"
 
-#define _XOPEN_SOURCE_EXTENDED
+#ifndef _XOPEN_SOURCE_EXTENDED
+# define _XOPEN_SOURCE_EXTENDED
+#endif
 
 #include <errno.h>
 
 #ifdef HAVE_FCNTL_H
 # include <fcntl.h>