diff --git a/ChangeLog b/ChangeLog
index b394998cc3..88e4cb2159 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jul 22 20:42:52 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/socket/extconf.rb: define IPPROTO_IPV6 macro for recent Windows
+	  SDK.
+
 Wed Jul 22 19:32:10 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ext/socket/mkconstants.rb: define IPV6_* constants only when INET6
diff --git a/ext/socket/extconf.rb b/ext/socket/extconf.rb
index 7908e62bc7..21f99b9848 100644
--- a/ext/socket/extconf.rb
+++ b/ext/socket/extconf.rb
@@ -324,6 +324,9 @@ have_func("getpeereid")
 have_header("ucred.h", headers)
 have_func("getpeerucred")
 
+# workaround for recent Windows SDK
+$defs << "-DIPPROTO_IPV6=IPPROTO_IPV6" if have_const("IPPROTO_IPV6") && !have_macro("IPPROTO_IPV6")
+
 $distcleanfiles << "constants.h" << "constdefs.*"
 
 if have_func(test_func)