--- src/iperf_api.c
+++ src/iperf_api.c
@@ -27,7 +27,6 @@
 #ifndef _GNU_SOURCE
 # define _GNU_SOURCE
 #endif
-#define __USE_GNU
 
 #include "iperf_config.h"
 
--- src/iperf_auth.c
+++ src/iperf_auth.c
@@ -25,6 +25,8 @@
  * for complete information.
  */
 
+#define _GNU_SOURCE
+
 #include "iperf_config.h"
 
 #include <string.h>