diff --git a/binding-mri/binding-util.h b/binding-mri/binding-util.h
index c3f54e3..f8718b2 100644
--- a/binding-mri/binding-util.h
+++ b/binding-mri/binding-util.h
@@ -160,12 +160,6 @@ wrapProperty(VALUE self, void *prop, const char *iv,
 	return propObj;
 }
 
-inline void
-wrapNilProperty(VALUE self, const char *iv)
-{
-	rb_iv_set(self, iv, Qnil);
-}
-
 /* Implemented: oSszfibn| */
 int
 rb_get_args(int argc, VALUE *argv, const char *format, ...);
diff --git a/binding-mri/plane-binding.cpp b/binding-mri/plane-binding.cpp
index 5d2c407..0680263 100644
--- a/binding-mri/plane-binding.cpp
+++ b/binding-mri/plane-binding.cpp
@@ -35,7 +35,6 @@ RB_METHOD(planeInitialize)
 
 	p->initDynAttribs();
 
-	wrapNilProperty(self, "bitmap");
 	wrapProperty(self, p->getColor(), "color", ColorType);
 	wrapProperty(self, p->getTone(), "tone", ToneType);
 
diff --git a/binding-mri/sprite-binding.cpp b/binding-mri/sprite-binding.cpp
index 427d7b8..0fa4b46 100644
--- a/binding-mri/sprite-binding.cpp
+++ b/binding-mri/sprite-binding.cpp
@@ -39,7 +39,6 @@ RB_METHOD(spriteInitialize)
 	/* Wrap property objects */
 	s->initDynAttribs();
 
-	wrapNilProperty(self, "bitmap");
 	wrapProperty(self, s->getSrcRect(), "src_rect", RectType);
 	wrapProperty(self, s->getColor(), "color", ColorType);
 	wrapProperty(self, s->getTone(), "tone", ToneType);
diff --git a/binding-mri/window-binding.cpp b/binding-mri/window-binding.cpp
index 1cd0ac3..ed61b11 100644
--- a/binding-mri/window-binding.cpp
+++ b/binding-mri/window-binding.cpp
@@ -34,8 +34,6 @@ RB_METHOD(windowInitialize)
 
 	w->initDynAttribs();
 
-	wrapNilProperty(self, "windowskin");
-	wrapNilProperty(self, "contents");
 	wrapProperty(self, w->getCursorRect(), "cursor_rect", RectType);
 
 	return self;
diff --git a/binding-mri/windowvx-binding.cpp b/binding-mri/windowvx-binding.cpp
index 17bdd77..21cc7c3 100644
--- a/binding-mri/windowvx-binding.cpp
+++ b/binding-mri/windowvx-binding.cpp
@@ -53,7 +53,6 @@ RB_METHOD(windowVXInitialize)
 
 	w->initDynAttribs();
 
-	wrapNilProperty(self, "windowskin");
 	wrapProperty(self, w->getTone(), "tone", ToneType);
 	wrapProperty(self, w->getCursorRect(), "cursor_rect", RectType);
 
diff --git a/binding-mruby/binding-util.h b/binding-mruby/binding-util.h
index 448bf4a..fd2e8d1 100644
--- a/binding-mruby/binding-util.h
+++ b/binding-mruby/binding-util.h
@@ -312,15 +312,6 @@ wrapProperty(mrb_state *mrb, mrb_value self,
 	               propObj);
 }
 
-inline void
-wrapNilProperty(mrb_state *mrb, mrb_value self, CommonSymbol iv)
-{
-	mrb_obj_iv_set(mrb,
-	               mrb_obj_ptr(self),
-	               getSym(mrb, iv),
-	               mrb_nil_value());
-}
-
 inline mrb_value
 getProperty(mrb_state *mrb, mrb_value self, CommonSymbol iv)
 {
diff --git a/binding-mruby/plane-binding.cpp b/binding-mruby/plane-binding.cpp
index 430250b..5ad4e25 100644
--- a/binding-mruby/plane-binding.cpp
+++ b/binding-mruby/plane-binding.cpp
@@ -36,7 +36,6 @@ MRB_METHOD(planeInitialize)
 	p->setColor(new Color);
 	p->setTone(new Tone);
 
-	wrapNilProperty(mrb, self, CSbitmap);
 	wrapProperty(mrb, self, p->getColor(), CScolor, ColorType);
 	wrapProperty(mrb, self, p->getTone(), CStone, ToneType);
 
diff --git a/binding-mruby/sprite-binding.cpp b/binding-mruby/sprite-binding.cpp
index ddfee1e..adc2f9b 100644
--- a/binding-mruby/sprite-binding.cpp
+++ b/binding-mruby/sprite-binding.cpp
@@ -39,7 +39,6 @@ MRB_METHOD(spriteInitialize)
 	s->setColor(new Color);
 	s->setTone(new Tone);
 
-	wrapNilProperty(mrb, self, CSbitmap);
 	wrapProperty(mrb, self, s->getSrcRect(), CSsrc_rect, RectType);
 	wrapProperty(mrb, self, s->getColor(), CScolor, ColorType);
 	wrapProperty(mrb, self, s->getTone(), CStone, ToneType);
diff --git a/binding-mruby/window-binding.cpp b/binding-mruby/window-binding.cpp
index ac2ece5..5ba9d64 100644
--- a/binding-mruby/window-binding.cpp
+++ b/binding-mruby/window-binding.cpp
@@ -33,8 +33,6 @@ MRB_METHOD(windowInitialize)
 	setPrivateData(self, w, WindowType);
 
 	w->setCursorRect(new Rect);
-	wrapNilProperty(mrb, self, CSwindowskin);
-	wrapNilProperty(mrb, self, CScontents);
 	wrapProperty(mrb, self, w->getCursorRect(), CScursor_rect, RectType);
 
 	return self;