diff --git a/src/mdata.h b/include/mruby/data.h
similarity index 99%
rename from src/mdata.h
rename to include/mruby/data.h
index 827f7c114..07e0f72cd 100644
--- a/src/mdata.h
+++ b/include/mruby/data.h
@@ -1,6 +1,6 @@
 /**********************************************************************
 
-  mdata.h -
+  data.h -
 
 
   Copyright (C) 2007 Yukihiro Matsumoto
diff --git a/src/array.c b/src/array.c
index 855a45aba..69f5fd8b3 100644
--- a/src/array.c
+++ b/src/array.c
@@ -2,7 +2,6 @@
 #include "mruby/array.h"
 #include <string.h>
 #include "mruby/string.h"
-#include "mdata.h"
 #include "mruby/class.h"
 
 #ifdef INCLUDE_REGEXP
diff --git a/src/encoding.h b/src/encoding.h
index 784d67f44..92e16e5f2 100644
--- a/src/encoding.h
+++ b/src/encoding.h
@@ -18,7 +18,7 @@ extern "C" {
 
 #include <stdarg.h>
 #include "oniguruma.h"
-#include "mdata.h"
+#include "mruby/data.h"
 
 int mrb_tolower(int c);
 int mrb_toupper(int c);
diff --git a/src/etc.c b/src/etc.c
index 8c98700a3..865992566 100644
--- a/src/etc.c
+++ b/src/etc.c
@@ -1,5 +1,4 @@
 #include "mruby.h"
-#include "mdata.h"
 #include "mruby/string.h"
 #include "error.h"
 #include "mruby/numeric.h"
diff --git a/src/gc.c b/src/gc.c
index e4b1f82ba..f4186f6e3 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -10,7 +10,7 @@
 #include <stdio.h>
 #include "mruby/struct.h"
 #include "mruby/proc.h"
-#include "mdata.h"
+#include "mruby/data.h"
 #include "mruby/numeric.h"
 
 /*
diff --git a/src/kernel.c b/src/kernel.c
index e5b2cab04..7a4a13501 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -14,7 +14,6 @@
 #include "ritehash.h"
 #include "error.h"
 #include "method.h"
-#include "mdata.h"
 
 #ifdef INCLUDE_REGEXP
 #include "re.h"
diff --git a/src/object.c b/src/object.c
index c60c2fb7b..0a31fa108 100644
--- a/src/object.c
+++ b/src/object.c
@@ -5,7 +5,6 @@
 #include "mruby/class.h"
 #include "method.h"
 #include "mruby/numeric.h"
-#include "mdata.h"
 
 #ifdef INCLUDE_REGEXP
   #define mrb_usascii_str_new2 mrb_usascii_str_new_cstr