diff --git a/ChangeLog b/ChangeLog
index 5587224cd7..c7e834e7bc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Feb 25 12:06:13 2014  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* win32/Makefile.sub: define PACKED_STRUCT.
+
 Mon Feb 24 21:41:56 2014  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* README.md, README.ja.md: removed (wrong) mode setting for emacs.
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index e64b70ec7a..03cf78110d 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -570,6 +570,8 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 !if $(MSC_VER) >= 1500
 #define RUBY_FUNCTION_NAME_STRING __FUNCTION__
 !endif
+#define PACKED_STRUCT
+#define PACKED_STRUCT_UNALIGNED
 #define RUBY_EXTERN extern __declspec(dllimport)
 #define HAVE_DECL_SYS_NERR 1
 #define HAVE_LIMITS_H 1