diff --git a/ChangeLog b/ChangeLog
index 29549926c0..6491b0a9b0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jul 19 13:26:25 2012  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/socket/extconf.rb: now enable IPv6 by default on mswin.
+
 Thu Jul 19 09:33:46 2012  Aaron Patterson <aaron@tenderlovemaking.com>
 
 	* ext/psych/emitter.c (initialize): allow a configuration object to be
diff --git a/ext/socket/extconf.rb b/ext/socket/extconf.rb
index 32e55d1c46..87409394ff 100644
--- a/ext/socket/extconf.rb
+++ b/ext/socket/extconf.rb
@@ -35,7 +35,7 @@ if have_header("arpa/inet.h")
 end
 
 ipv6 = false
-default_ipv6 = /mswin|cygwin|beos|haiku/ !~ RUBY_PLATFORM
+default_ipv6 = /cygwin|beos|haiku/ !~ RUBY_PLATFORM
 if enable_config("ipv6", default_ipv6)
   if checking_for("ipv6") {try_link(<<EOF)}
 #include <sys/types.h>