diff --git a/mrbgems/mruby-metaprog/src/metaprog.c b/mrbgems/mruby-metaprog/src/metaprog.c
index f1fe097c7..9e962b4a1 100644
--- a/mrbgems/mruby-metaprog/src/metaprog.c
+++ b/mrbgems/mruby-metaprog/src/metaprog.c
@@ -6,6 +6,7 @@
 #include "mruby/class.h"
 #include "mruby/string.h"
 #include <mruby/internal.h>
+#include "mruby/khash.h"
 #include "mruby/presym.h"
 
 typedef enum {