diff --git a/asc2log.c b/asc2log.c
index 71be7f8..8c6c24c 100644
--- a/asc2log.c
+++ b/asc2log.c
@@ -42,6 +42,10 @@
  *
  */
 
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
 #include <libgen.h>
 #include <locale.h>
 #include <stdio.h>