diff --git a/ChangeLog b/ChangeLog
index e839f9a215..72c5ec1593 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Feb  9 02:04:03 2009  Tanaka Akira  <akr@fsij.org>
+
+	* ext/socket/option.c (inspect_peercred): struct ucred contains
+	  effective uid/gid.
+
 Mon Feb  9 00:44:45 2009  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/option.c (sockopt_inspect): add ifdef guard for
diff --git a/ext/socket/option.c b/ext/socket/option.c
index 980acda85d..36750ad6c0 100644
--- a/ext/socket/option.c
+++ b/ext/socket/option.c
@@ -246,7 +246,7 @@ inspect_peercred(int level, int optname, VALUE data, VALUE ret)
     if (RSTRING_LEN(data) == sizeof(struct ucred)) {
         struct ucred cred;
         memcpy(&cred, RSTRING_PTR(data), sizeof(struct ucred));
-        rb_str_catf(ret, " pid=%u uid=%u gid=%u", cred.pid, cred.uid, cred.gid);
+        rb_str_catf(ret, " pid=%u euid=%u egid=%u", cred.pid, cred.uid, cred.gid);
         rb_str_cat2(ret, " (ucred)");
         return 0;
     }
diff --git a/test/socket/test_unix.rb b/test/socket/test_unix.rb
index fb0c47d348..663ad8f111 100644
--- a/test/socket/test_unix.rb
+++ b/test/socket/test_unix.rb
@@ -306,8 +306,8 @@ class TestUNIXSocket < Test::Unit::TestCase
       cred = s.getsockopt(:SOCKET, :PEERCRED)
       inspect = cred.inspect
       assert_match(/ pid=#{$$} /, inspect)
-      assert_match(/ uid=#{Process.uid} /, inspect)
-      assert_match(/ gid=#{Process.gid} /, inspect)
+      assert_match(/ euid=#{Process.euid} /, inspect)
+      assert_match(/ egid=#{Process.egid} /, inspect)
       assert_match(/ \(ucred\)/, inspect)
     }
   end