diff --git a/build/rmkdepend/main.c b/build/rmkdepend/main.c
index 20e77e542317d6101d6323d46701c04ef43b3274..a4e9dd37f4c9fb6ffeff1ccca4919c414e4b874f 100644
--- a/build/rmkdepend/main.c
+++ b/build/rmkdepend/main.c
@@ -28,7 +28,7 @@ in this Software without prior written authorization from the X Consortium.
 */
 
 #if !defined(USGISH) || !defined(_SEQUENT_) || !defined(USE_CHMOD)
-#define _BSD_SOURCE /* def.h includes sys/stat and we need _BSD_SOURCE for fchmod see man fchmod */
+#define _DEFAULT_SOURCE /* def.h includes sys/stat and we need _BSD_SOURCE for fchmod see man fchmod */
 #endif
 
 #include "def.h"