diff --git a/ChangeLog b/ChangeLog
index 6d50be15e0..b394998cc3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jul 22 19:32:10 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* ext/socket/mkconstants.rb: define IPV6_* constants only when INET6
+	  is defined.
+
 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.
diff --git a/ext/socket/mkconstants.rb b/ext/socket/mkconstants.rb
index 3074a8ff8d..6df8fbeaf9 100644
--- a/ext/socket/mkconstants.rb
+++ b/ext/socket/mkconstants.rb
@@ -56,7 +56,7 @@ def each_const
       make_value = "INT2NUM"
     end
     guard = nil
-    if /\A(AF_INET6|PF_INET6)\z/ =~ name
+    if /\A(AF_INET6|PF_INET6|IPV6_.*)\z/ =~ name
       # IPv6 is not supported although AF_INET6 is defined on bcc32/mingw
       guard = "defined(INET6)"
     end