diff --git a/ChangeLog b/ChangeLog
index 4b3f158900..44894cd50d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,7 @@
-Tue Apr  9 02:42:44 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Tue Apr  9 02:44:32 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/socket/extconf.rb: $defs needs -D or -U.  nothing is added
+	  otherwize.
 
 	* ext/socket/extconf.rb: check struct in_addr6, which is defined in
 	  VC6 instead of in6_addr.
diff --git a/ext/socket/extconf.rb b/ext/socket/extconf.rb
index a168404ae3..e8b2d39ae2 100644
--- a/ext/socket/extconf.rb
+++ b/ext/socket/extconf.rb
@@ -482,7 +482,7 @@ EOS
       $defs << "-Din_addr6=in6_addr"
     end
     if have_struct_member("struct in6_addr", "s6_addr8", headers)
-      $defs[-1] = "s6_addr=s6_addr8"
+      $defs[-1] = "-Ds6_addr=s6_addr8"
     end
     if ipv6 == "kame" && have_struct_member("struct in6_addr", "s6_addr32", headers)
       $defs[-1] = "-DFAITH"