diff --git a/ChangeLog b/ChangeLog
index a089758705..f244c689ee 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jan 12 23:31:42 2009  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/socket.c (IS_IP_FAMILY): defined.
+	  (addrinfo_ip_p): use it.
+
 Mon Jan 12 17:23:05 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/test/unit/assertions.rb (assert_nothing_raised): removes the
diff --git a/ext/socket/socket.c b/ext/socket/socket.c
index 08276bf8b6..afec72e59a 100644
--- a/ext/socket/socket.c
+++ b/ext/socket/socket.c
@@ -5106,6 +5106,12 @@ addrinfo_canonname(VALUE self)
     return rai->canonname;
 }
 
+#ifdef AF_INET6
+# define IS_IP_FAMILY(af) ((af) == AF_INET || (af) == AF_INET6)
+#else
+# define IS_IP_FAMILY(af) ((af) == AF_INET)
+#endif
+
 /*
  * call-seq:
  *   addrinfo.ip? => true or false
@@ -5123,12 +5129,7 @@ addrinfo_ip_p(VALUE self)
 {
     rb_addrinfo_t *rai = get_addrinfo(self);
     int family = ai_get_afamily(rai);
-    return family == AF_INET
-#ifdef AF_INET6
-        || family == AF_INET6
-#endif
-        ? Qtrue : Qfalse;
-    return Qfalse;
+    return IS_IP_FAMILY(family) ? Qtrue : Qfalse;
 }
 
 /*