diff --git a/binding-mruby/mrb-ext/rwmem.cpp b/binding-mruby/mrb-ext/rwmem.cpp
index 1c83061..1c027b7 100644
--- a/binding-mruby/mrb-ext/rwmem.cpp
+++ b/binding-mruby/mrb-ext/rwmem.cpp
@@ -20,6 +20,7 @@
 */
 
 #include "rwmem.h"
+#include "util.h"
 
 #include <SDL_rwops.h>