diff --git a/srcpos.c b/srcpos.c
index 4fdb22a..87ddf8d 100644
--- a/srcpos.c
+++ b/srcpos.c
@@ -3,7 +3,9 @@
  * Copyright 2007 Jon Loeliger, Freescale Semiconductor, Inc.
  */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 
 #include <stdio.h>
 
diff --git a/tests/testutils.c b/tests/testutils.c
index 10129c0..d1ddee3 100644
--- a/tests/testutils.c
+++ b/tests/testutils.c
@@ -5,7 +5,9 @@
  * Copyright (C) 2006 David Gibson, IBM Corporation.
  */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE /* for strsignal() in glibc.  FreeBSD has it either way */
+#endif
 
 #include <stdio.h>
 #include <stdlib.h>