diff --git a/include/mruby/khash.h b/include/mruby/khash.h
index 9eddc0bb3..839221e84 100644
--- a/include/mruby/khash.h
+++ b/include/mruby/khash.h
@@ -11,6 +11,7 @@
 extern "C" {
 #endif
 
+#include "mruby.h"
 #include <stdint.h>
 #include <string.h>