diff --git a/src/variable.c b/src/variable.c
index 0bc1f0de1..870c96a6a 100644
--- a/src/variable.c
+++ b/src/variable.c
@@ -1,3 +1,4 @@
+#include <stdio.h>
 #include "mruby.h"
 #include "mruby/class.h"
 #include "ritehash.h"