diff --git a/ChangeLog b/ChangeLog
index 98dc8777b1..ae483a815f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Thu Jun 18 16:58:35 2015  Koichi Sasada  <ko1@atdot.net>
+
+	* method.h: constify rb_method_alias_struct::original_me and
+	  rb_method_refined_struct::orig_me.
+
+	* class.c (move_refined_method): use RB_OBJ_WRITE() for 
+	  me->def->body.refined.orig_me.
+
 Thu Jun 18 14:35:28 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* ext/objspace/objspace.c (count_imemo_objects): support imemo_ment.
diff --git a/class.c b/class.c
index b8b44c96f6..f963f0c22a 100644
--- a/class.c
+++ b/class.c
@@ -915,7 +915,7 @@ move_refined_method(st_data_t key, st_data_t value, st_data_t data)
     if (me->def->type == VM_METHOD_TYPE_REFINED) {
 	if (me->def->body.refined.orig_me) {
 	    const rb_method_entry_t *orig_me = me->def->body.refined.orig_me, *new_me;
-	    me->def->body.refined.orig_me = NULL;
+	    RB_OBJ_WRITE(me, &me->def->body.refined.orig_me, NULL);
 	    new_me = rb_method_entry_clone(me);
 	    st_add_direct(tbl, key, (st_data_t) new_me);
 	    rb_method_entry_copy(me, orig_me);
diff --git a/method.h b/method.h
index bd717eb3d1..4badd06db5 100644
--- a/method.h
+++ b/method.h
@@ -122,11 +122,11 @@ typedef struct rb_method_attr_struct {
 } rb_method_attr_t;
 
 typedef struct rb_method_alias_struct {
-    const struct rb_method_entry_struct *original_me; /* original_me->klass is original owner */
+    const struct rb_method_entry_struct * const original_me; /* original_me->klass is original owner */
 } rb_method_alias_t;
 
 typedef struct rb_method_refined_struct {
-    const struct rb_method_entry_struct *orig_me;
+    const struct rb_method_entry_struct * const orig_me;
 } rb_method_refined_t;
 
 typedef struct rb_method_definition_struct {