diff --git a/src/REAL.c b/src/REAL.c
index e179152..2994b74 100644
--- a/src/REAL.c
+++ b/src/REAL.c
@@ -3,7 +3,7 @@
  * Redistribution and modifications are permitted subject to BSD license.
  */
 #define	_ISOC99_SOURCE		/* For ilogb() and quiet NAN */
-#define	_BSD_SOURCE		/* To reintroduce finite(3) */
+#define	_DEFAULT_SOURCE		/* To reintroduce finite(3) */
 #if	defined(__alpha)
 #include <sys/resource.h>	/* For INFINITY */
 #endif