diff --git a/examples/app.c b/examples/app.c
index abb45aa6..03adf85d 100644
--- a/examples/app.c
+++ b/examples/app.c
@@ -5,7 +5,9 @@
  * to the capture from your application.
  */
 
-#define _GNU_SOURCE
+#ifndef _GNU_SOURCE
+# define _GNU_SOURCE
+#endif
 
 #ifdef __linux__
 # include <sched.h>