diff --git a/src/libmdb/data.c b/src/libmdb/data.c
index bc3950b..ce09bda 100644
--- a/src/libmdb/data.c
+++ b/src/libmdb/data.c
@@ -18,9 +18,6 @@
 
 #include "mdbtools.h"
 
-#ifndef _XOPEN_SOURCE
-#define _XOPEN_SOURCE
-#endif
 #include <time.h>
 
 #define OFFSET_MASK 0x1fff