diff --git a/lib/utils/mu-utils.cc b/lib/utils/mu-utils.cc
index e641450d..2c2e86c6 100644
--- a/lib/utils/mu-utils.cc
+++ b/lib/utils/mu-utils.cc
@@ -17,7 +17,10 @@
 **  02110-1301, USA.
 */
 
+#ifndef _XOPEN_SOURCE
 #define _XOPEN_SOURCE
+#endif /*_XOPEN_SOURCE*/
+
 #include <time.h>
 
 #define GNU_SOURCE