diff --git a/loop.c b/loop.c
index f23f0f3..3375756 100644
--- a/loop.c
+++ b/loop.c
@@ -21,6 +21,7 @@
 #include "config.h"
 #endif
 
+#define _GNU_SOURCE
 #define READLINE_CALLBACKS
 
 #include <assert.h>