diff --git a/ChangeLog b/ChangeLog
index 0aba67c96e..3fdb9f4961 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Nov 29 16:14:50 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* error.c (rb_typeddata_is_kind_of, rb_check_typeddata): ditto.
+
+	* error.c (rb_typeddata_inherited_p): deprecate. still keep for
+	  potential binary compatibility.
+
 Sat Nov 29 10:49:23 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* win32/win32.c (win32_direct_conv, rb_w32_readdir): convert UTF-8
diff --git a/error.c b/error.c
index 375c2ff5a7..81684a112d 100644
--- a/error.c
+++ b/error.c
@@ -541,10 +541,8 @@ rb_check_type(VALUE x, int t)
 int
 rb_typeddata_inherited_p(const rb_data_type_t *child, const rb_data_type_t *parent)
 {
-    while (child) {
-	if (child == parent) return 1;
-	child = child->parent;
-    }
+    rb_warn("rb_typeddata_inherited_p() is deprecated");
+    if (child == parent) return 1;
     return 0;
 }
 
@@ -552,7 +550,7 @@ int
 rb_typeddata_is_kind_of(VALUE obj, const rb_data_type_t *data_type)
 {
     if (!RB_TYPE_P(obj, T_DATA) ||
-	!RTYPEDDATA_P(obj) || !rb_typeddata_inherited_p(RTYPEDDATA_TYPE(obj), data_type)) {
+	!RTYPEDDATA_P(obj) || RTYPEDDATA_TYPE(obj) != data_type) {
 	return 0;
     }
     return 1;
@@ -572,7 +570,7 @@ rb_check_typeddata(VALUE obj, const rb_data_type_t *data_type)
 	etype = rb_obj_classname(obj);
 	rb_raise(rb_eTypeError, mesg, etype, data_type->wrap_struct_name);
     }
-    else if (!rb_typeddata_inherited_p(RTYPEDDATA_TYPE(obj), data_type)) {
+    else if (RTYPEDDATA_TYPE(obj) != data_type) {
 	etype = RTYPEDDATA_TYPE(obj)->wrap_struct_name;
 	rb_raise(rb_eTypeError, mesg, etype, data_type->wrap_struct_name);
     }
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index fb51132f65..635076fb13 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -973,7 +973,7 @@ struct rb_data_type_struct {
 	void *reserved[2]; /* For future extension.
 			      This array *must* be filled with ZERO. */
     } function;
-    const rb_data_type_t *parent;
+    void *const reserved;
     void *data;        /* This area can be used for any purpose
                           by a programmer who define the type. */
     VALUE flags;       /* FL_WB_PROTECTED */
@@ -981,7 +981,6 @@ struct rb_data_type_struct {
 
 #define HAVE_TYPE_RB_DATA_TYPE_T 1
 #define HAVE_RB_DATA_TYPE_T_FUNCTION 1
-#define HAVE_RB_DATA_TYPE_T_PARENT 1
 
 struct RTypedData {
     struct RBasic basic;
@@ -1010,7 +1009,6 @@ typedef void (*RUBY_DATA_FUNC)(void*);
 #endif
 VALUE rb_data_object_alloc(VALUE,void*,RUBY_DATA_FUNC,RUBY_DATA_FUNC);
 VALUE rb_data_typed_object_alloc(VALUE klass, void *datap, const rb_data_type_t *);
-int rb_typeddata_inherited_p(const rb_data_type_t *child, const rb_data_type_t *parent);
 int rb_typeddata_is_kind_of(VALUE, const rb_data_type_t *);
 void *rb_check_typeddata(VALUE, const rb_data_type_t *);
 #define Check_TypedStruct(v,t) rb_check_typeddata((VALUE)(v),(t))