diff --git a/ChangeLog b/ChangeLog
index ed76f4d00c..6d50be15e0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jul 22 19:23:04 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/socket/extconf.rb: ipv6 support is disabled by default on mswin.
+
 Wed Jul 22 17:41:08 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* ext/socket/ipsocket.c (init_inetsock_internal): drop IPv6 addresses
diff --git a/ext/socket/extconf.rb b/ext/socket/extconf.rb
index 548abd4f7c..7908e62bc7 100644
--- a/ext/socket/extconf.rb
+++ b/ext/socket/extconf.rb
@@ -33,7 +33,7 @@ if have_header("arpa/inet.h")
 end
 
 ipv6 = false
-default_ipv6 = /cygwin|beos|haiku/ !~ RUBY_PLATFORM
+default_ipv6 = /mswin|cygwin|beos|haiku/ !~ RUBY_PLATFORM
 if enable_config("ipv6", default_ipv6)
   if checking_for("ipv6") {try_link(<<EOF)}
 #include <sys/types.h>