diff --git a/binding-mri/binding-util.cpp b/binding-mri/binding-util.cpp
index 4dc6fc9..d70a039 100644
--- a/binding-mri/binding-util.cpp
+++ b/binding-mri/binding-util.cpp
@@ -29,19 +29,6 @@
 #include <string.h>
 #include <assert.h>
 
-void initType(rb_data_type_t &type,
-              const char *name,
-              void (*freeInst)(void *))
-{
-	type.wrap_struct_name = name;
-	type.function.dmark = 0;
-	type.function.dsize = 0;
-	type.function.dfree = freeInst;
-	type.function.reserved[0] =
-	type.function.reserved[1] = 0;
-	type.parent = 0;
-}
-
 RbData *getRbData()
 {
 	return static_cast<RbData*>(shState->bindingData());
diff --git a/binding-mri/binding-util.h b/binding-mri/binding-util.h
index 93fe006..703d525 100644
--- a/binding-mri/binding-util.h
+++ b/binding-mri/binding-util.h
@@ -64,12 +64,27 @@ raiseRbExc(const Exception &exc);
 #define DECL_TYPE(Klass) \
 	extern rb_data_type_t Klass##Type
 
-#define DEF_TYPE(Klass) \
-	rb_data_type_t Klass##Type
+/* 2.1 has added a new field (flags) to rb_data_type_t */
+#include <ruby/version.h>
+#if RUBY_API_VERSION_MINOR > 0
+/* TODO: can mkxp use RUBY_TYPED_FREE_IMMEDIATELY here? */
+#define DEF_TYPE_FLAGS 0
+#else
+#define DEF_TYPE_FLAGS
+#endif
 
-void initType(rb_data_type_t &type,
-              const char *name,
-              void (*freeInst)(void*));
+#define DEF_TYPE_CUSTOMNAME_AND_FREE(Klass, Name, Free) \
+	rb_data_type_t Klass##Type = { \
+		Name, { 0, Free, 0, { 0, 0 } }, 0, 0, DEF_TYPE_FLAGS \
+	}
+
+#define DEF_TYPE_CUSTOMFREE(Klass, Free) \
+	DEF_TYPE_CUSTOMNAME_AND_FREE(Klass, #Klass, Free)
+
+#define DEF_TYPE_CUSTOMNAME(Klass, Name) \
+	DEF_TYPE_CUSTOMNAME_AND_FREE(Klass, Name, freeInstance<Klass>)
+
+#define DEF_TYPE(Klass) DEF_TYPE_CUSTOMNAME(Klass, #Klass)
 
 template<rb_data_type_t *rbType>
 static VALUE classAllocate(VALUE klass)
@@ -83,8 +98,6 @@ static void freeInstance(void *inst)
 	delete static_cast<C*>(inst);
 }
 
-#define INIT_TYPE(Klass) initType(Klass##Type, #Klass, freeInstance<Klass>)
-
 void
 raiseDisposedAccess(VALUE self);
 
diff --git a/binding-mri/bitmap-binding.cpp b/binding-mri/bitmap-binding.cpp
index a5652f8..e7ef5d4 100644
--- a/binding-mri/bitmap-binding.cpp
+++ b/binding-mri/bitmap-binding.cpp
@@ -427,8 +427,6 @@ INITCOPY_FUN(Bitmap)
 void
 bitmapBindingInit()
 {
-	INIT_TYPE(Bitmap);
-
 	VALUE klass = rb_define_class("Bitmap", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&BitmapType>);
 
diff --git a/binding-mri/etc-binding.cpp b/binding-mri/etc-binding.cpp
index 91c250f..32ad494 100644
--- a/binding-mri/etc-binding.cpp
+++ b/binding-mri/etc-binding.cpp
@@ -169,7 +169,6 @@ INITCOPY_FUN(Rect)
 
 #define INIT_BIND(Klass) \
 { \
-	INIT_TYPE(Klass); \
 	klass = rb_define_class(#Klass, rb_cObject); \
 	rb_define_alloc_func(klass, classAllocate<&Klass##Type>); \
 	rb_define_class_method(klass, "_load", Klass##Load); \
diff --git a/binding-mri/filesystem-binding.cpp b/binding-mri/filesystem-binding.cpp
index b8100d2..42bcec3 100644
--- a/binding-mri/filesystem-binding.cpp
+++ b/binding-mri/filesystem-binding.cpp
@@ -28,7 +28,16 @@
 #include "ruby/encoding.h"
 #include "ruby/intern.h"
 
-DEF_TYPE(FileInt);
+static void
+fileIntFreeInstance(void *inst)
+{
+	SDL_RWops *ops = static_cast<SDL_RWops*>(inst);
+
+	SDL_RWclose(ops);
+	SDL_FreeRW(ops);
+}
+
+DEF_TYPE_CUSTOMFREE(FileInt, fileIntFreeInstance);
 
 static VALUE
 fileIntForPath(const char *path)
@@ -100,15 +109,6 @@ RB_METHOD(fileIntBinmode)
 	return Qnil;
 }
 
-static void
-fileIntFreeInstance(void *inst)
-{
-	SDL_RWops *ops = static_cast<SDL_RWops*>(inst);
-
-	SDL_RWclose(ops);
-	SDL_FreeRW(ops);
-}
-
 VALUE
 kernelLoadDataInt(const char *filename)
 {
@@ -196,8 +196,6 @@ RB_METHOD(_marshalLoad)
 void
 fileIntBindingInit()
 {
-	initType(FileIntType, "FileInt", fileIntFreeInstance);
-
 	VALUE klass = rb_define_class("FileInt", rb_cIO);
 	rb_define_alloc_func(klass, classAllocate<&FileIntType>);
 
diff --git a/binding-mri/font-binding.cpp b/binding-mri/font-binding.cpp
index abf0581..c33e138 100644
--- a/binding-mri/font-binding.cpp
+++ b/binding-mri/font-binding.cpp
@@ -260,8 +260,6 @@ RB_METHOD(FontSetDefaultColor)
 void
 fontBindingInit()
 {
-	INIT_TYPE(Font);
-
 	VALUE klass = rb_define_class("Font", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&FontType>);
 
diff --git a/binding-mri/plane-binding.cpp b/binding-mri/plane-binding.cpp
index d1426a2..0cbb48f 100644
--- a/binding-mri/plane-binding.cpp
+++ b/binding-mri/plane-binding.cpp
@@ -59,8 +59,6 @@ DEF_PROP_F(Plane, ZoomY)
 void
 planeBindingInit()
 {
-	INIT_TYPE(Plane);
-
 	VALUE klass = rb_define_class("Plane", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&PlaneType>);
 
diff --git a/binding-mri/sprite-binding.cpp b/binding-mri/sprite-binding.cpp
index 6dea6f5..830ef87 100644
--- a/binding-mri/sprite-binding.cpp
+++ b/binding-mri/sprite-binding.cpp
@@ -99,8 +99,6 @@ RB_METHOD(spriteHeight)
 void
 spriteBindingInit()
 {
-	INIT_TYPE(Sprite);
-
 	VALUE klass = rb_define_class("Sprite", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&SpriteType>);
 
diff --git a/binding-mri/table-binding.cpp b/binding-mri/table-binding.cpp
index 9a29079..97831f2 100644
--- a/binding-mri/table-binding.cpp
+++ b/binding-mri/table-binding.cpp
@@ -147,8 +147,6 @@ INITCOPY_FUN(Table)
 void
 tableBindingInit()
 {
-	INIT_TYPE(Table);
-
 	VALUE klass = rb_define_class("Table", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&TableType>);
 
diff --git a/binding-mri/tilemap-binding.cpp b/binding-mri/tilemap-binding.cpp
index a62cca2..58674b9 100644
--- a/binding-mri/tilemap-binding.cpp
+++ b/binding-mri/tilemap-binding.cpp
@@ -28,7 +28,7 @@
 #include "binding-util.h"
 #include "binding-types.h"
 
-rb_data_type_t TilemapAutotilesType;
+DEF_TYPE_CUSTOMFREE(TilemapAutotiles, RUBY_TYPED_NEVER_FREE);
 
 RB_METHOD(tilemapAutotilesSet)
 {
@@ -137,16 +137,12 @@ DEF_PROP_I(Tilemap, OY)
 void
 tilemapBindingInit()
 {
-	initType(TilemapAutotilesType, "TilemapAutotiles", 0);
-
 	VALUE klass = rb_define_class("TilemapAutotiles", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&TilemapAutotilesType>);
 
 	_rb_define_method(klass, "[]=", tilemapAutotilesSet);
 	_rb_define_method(klass, "[]", tilemapAutotilesGet);
 
-	INIT_TYPE(Tilemap);
-
 	klass = rb_define_class("Tilemap", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&TilemapType>);
 
diff --git a/binding-mri/tilemapvx-binding.cpp b/binding-mri/tilemapvx-binding.cpp
index d87d16b..7e51d2f 100644
--- a/binding-mri/tilemapvx-binding.cpp
+++ b/binding-mri/tilemapvx-binding.cpp
@@ -29,8 +29,9 @@
 #include "binding-util.h"
 #include "binding-types.h"
 
-DEF_TYPE(TilemapVX);
-rb_data_type_t BitmapArrayType;
+DEF_TYPE_CUSTOMNAME(TilemapVX, "Tilemap");
+
+DEF_TYPE_CUSTOMFREE(BitmapArray, RUBY_TYPED_NEVER_FREE);
 
 RB_METHOD(tilemapVXInitialize)
 {
@@ -130,8 +131,6 @@ RB_METHOD(tilemapVXBitmapsGet)
 void
 tilemapVXBindingInit()
 {
-	initType(TilemapVXType, "Tilemap", freeInstance<TilemapVX>);
-
 	VALUE klass = rb_define_class("Tilemap", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&TilemapVXType>);
 
@@ -157,8 +156,6 @@ tilemapVXBindingInit()
 	INIT_PROP_BIND( TilemapVX, Flags,     "passages"   );
 	}
 
-	initType(BitmapArrayType, "BitmapArray", 0);
-
 	klass = rb_define_class_under(klass, "BitmapArray", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&BitmapArrayType>);
 
diff --git a/binding-mri/viewport-binding.cpp b/binding-mri/viewport-binding.cpp
index 2cd6fd4..612ac16 100644
--- a/binding-mri/viewport-binding.cpp
+++ b/binding-mri/viewport-binding.cpp
@@ -89,8 +89,6 @@ DEF_PROP_I(Viewport, OY)
 void
 viewportBindingInit()
 {
-	INIT_TYPE(Viewport);
-
 	VALUE klass = rb_define_class("Viewport", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&ViewportType>);
 
diff --git a/binding-mri/window-binding.cpp b/binding-mri/window-binding.cpp
index 0fddf6c..5df0e7b 100644
--- a/binding-mri/window-binding.cpp
+++ b/binding-mri/window-binding.cpp
@@ -73,8 +73,6 @@ DEF_PROP_I(Window, ContentsOpacity)
 void
 windowBindingInit()
 {
-	INIT_TYPE(Window);
-
 	VALUE klass = rb_define_class("Window", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&WindowType>);
 
diff --git a/binding-mri/windowvx-binding.cpp b/binding-mri/windowvx-binding.cpp
index b698a58..d70f02e 100644
--- a/binding-mri/windowvx-binding.cpp
+++ b/binding-mri/windowvx-binding.cpp
@@ -26,7 +26,7 @@
 
 #include "bitmap.h"
 
-DEF_TYPE(WindowVX);
+DEF_TYPE_CUSTOMNAME(WindowVX, "Window");
 
 void bitmapInitProps(Bitmap *b, VALUE self);
 
@@ -135,9 +135,6 @@ DEF_PROP_B(WindowVX, Pause)
 void
 windowVXBindingInit()
 {
-	// FIXME: data type name will end up as "WindowVX"
-	INIT_TYPE(WindowVX);
-
 	VALUE klass = rb_define_class("Window", rb_cObject);
 	rb_define_alloc_func(klass, classAllocate<&WindowVXType>);