diff --git a/ChangeLog b/ChangeLog
index 989e423e33..c27111d309 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Feb  2 17:11:23 2009  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/ancdata.c (cmsg_type_to_sym): add #ifdef for no IPv6
+	  environment.
+
 Mon Feb  2 17:05:55 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* file.c (rb_find_file_ext): should not be infected from other
diff --git a/ext/socket/ancdata.c b/ext/socket/ancdata.c
index 0d40d5bf10..5cc5c49d98 100644
--- a/ext/socket/ancdata.c
+++ b/ext/socket/ancdata.c
@@ -22,8 +22,10 @@ cmsg_type_to_sym(int level, int cmsg_type)
         return constant_to_sym(cmsg_type, intern_scm_optname);
       case IPPROTO_IP:
         return constant_to_sym(cmsg_type, intern_ip_optname);
+#ifdef IPPROTO_IPV6
       case IPPROTO_IPV6:
         return constant_to_sym(cmsg_type, intern_ipv6_optname);
+#endif
       case IPPROTO_TCP:
         return constant_to_sym(cmsg_type, intern_tcp_optname);
       case IPPROTO_UDP: