diff --git a/ChangeLog b/ChangeLog
index 6b8abc5129..ed53ba3e5b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Oct 27 09:57:56 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* include/ruby/ruby.h (SIZE_MAX): define SIZE_MAX if not defined.
+	  patched by The Written Word Inc. [ruby-core:40422] [Bug #5489]
+
 Thu Oct 27 08:47:38 2011  Martin Bosslet  <Martin.Bosslet@googlemail.com>
 
 	* ext/psych/parser.c: remove unused variable.
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 50b20845f1..c9544fa510 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -258,6 +258,22 @@ VALUE rb_ull2inum(unsigned LONG_LONG);
 # define SSIZET2NUM(v) INT2NUM(v)
 #endif
 
+#ifndef SIZE_MAX
+# if SIZEOF_SIZE_T > SIZEOF_LONG && defined(HAVE_LONG_LONG)
+#   define SIZE_MAX ULLONG_MAX
+#   define SIZE_MIN ULLONG_MIN
+# elif SIZEOF_SIZE_T == SIZEOF_LONG
+#   define SIZE_MAX ULONG_MAX
+#   define SIZE_MIN ULONG_MIN
+# elif SIZEOF_SIZE_T == SIZEOF_INT
+#   define SIZE_MAX UINT_MAX
+#   define SIZE_MIN UINT_MIN
+# else
+#   define SIZE_MAX USHRT_MAX
+#   define SIZE_MIN USHRT_MIN
+# endif
+#endif
+
 #ifndef SSIZE_MAX
 # if SIZEOF_SIZE_T > SIZEOF_LONG && defined(HAVE_LONG_LONG)
 #   define SSIZE_MAX LLONG_MAX