diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index 82e0d2f7a..ebef56051 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -10,6 +10,9 @@
 #include <mruby/array.h>
 #include <mruby/string.h>
 #include <mruby/internal.h>
+#ifdef MRB_DEBUG
+#include <mruby/hash.h>
+#endif
 #include <string.h>
 #include "bigint.h"