diff --git a/ChangeLog b/ChangeLog
index 68e5699d82..f4b8595166 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Thu Feb  3 16:31:43 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* include/ruby/missing.h: don't use HAVE_STDDEF_H because it never
+	  defined by configure though configure.bat defines it.
+
+	* include/ruby/ruby.h: move include stddef.h to defines.h
+
+	* include/ruby/defines.h: ditto.
+
 Wed Feb  2 20:25:04 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* include/ruby/encoding.h (rb_enc_step_back): cast 4th argument 'n'
diff --git a/include/ruby/defines.h b/include/ruby/defines.h
index ef2dbfeff1..255b4aeee9 100644
--- a/include/ruby/defines.h
+++ b/include/ruby/defines.h
@@ -24,7 +24,10 @@ extern "C" {
 
 #define RUBY
 
-#include <stdlib.h>
+# include <stddef.h>
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
 #ifdef __cplusplus
 # ifndef  HAVE_PROTOTYPES
 #  define HAVE_PROTOTYPES 1
diff --git a/include/ruby/missing.h b/include/ruby/missing.h
index abbd2bf870..660edb529d 100644
--- a/include/ruby/missing.h
+++ b/include/ruby/missing.h
@@ -19,9 +19,7 @@ extern "C" {
 #endif
 
 #include "ruby/config.h"
-#if defined(HAVE_STDDEF_H)
-#  include <stddef.h>
-#endif
+#include <stddef.h>
 #ifdef RUBY_EXTCONF_H
 #include RUBY_EXTCONF_H
 #endif
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 8ecb0f2405..afa181509a 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -44,10 +44,6 @@ extern "C" {
 #define PRINTF_ARGS(decl, string_index, first_to_check) decl
 #endif
 
-#ifdef HAVE_STDLIB_H
-# include <stdlib.h>
-#endif
-
 #ifdef HAVE_STRING_H
 # include <string.h>
 #else
@@ -66,7 +62,6 @@ extern "C" {
 #endif
 
 #include <stdarg.h>
-#include <stddef.h>
 #include <stdio.h>
 
 #include "defines.h"