diff --git a/ChangeLog b/ChangeLog
index f039de00d1..6c71fe9cf1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri May  3 14:09:45 2013  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/extconf.rb: Make default_ipv6 true for Cygwin.
+	  Cygwin supports IPv6 since Cygwin 1.7.1 (2009-12).
+	  http://cygwin.com/ml/cygwin-announce/2009-12/msg00027.html
+
 Fri May  3 13:35:26 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/socket/{getaddrinfo,getnameinfo}.c: define socklen_t if not
diff --git a/ext/socket/extconf.rb b/ext/socket/extconf.rb
index f74d601063..66fb06d7c6 100644
--- a/ext/socket/extconf.rb
+++ b/ext/socket/extconf.rb
@@ -427,7 +427,7 @@ EOF
   end
 
   ipv6 = false
-  default_ipv6 = /cygwin|beos|haiku/ !~ RUBY_PLATFORM
+  default_ipv6 = /beos|haiku/ !~ RUBY_PLATFORM
   if enable_config("ipv6", default_ipv6)
     if checking_for("ipv6") {try_link(AF_INET6_SOCKET_CREATION_TEST)}
       $defs << "-DENABLE_IPV6" << "-DINET6"