diff --git a/ChangeLog b/ChangeLog
index e1bc00dd0b..ac0dd61c06 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Sep 16 09:20:42 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* test/ruby/test_io.rb (TestIO#test_dup): exception should be
+	  raised from IO#dup.
+
 Tue Sep 16 08:35:29 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* test/ruby/test_io.rb (TestIO#test_dup): this test might fail if
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index a82cac239b..ba85b847be 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -632,6 +632,9 @@ class TestIO < Test::Unit::TestCase
     assert_raise(Errno::EMFILE, Errno::ENFILE, Errno::ENOMEM) do
       loop {a << IO.pipe}
     end
+    assert_raise(Errno::EMFILE, Errno::ENFILE, Errno::ENOMEM) do
+      loop {a[-1][0].dup; a[-1][1].dup}
+    end
     a.each do |r, w|
       r.close unless !r || r.closed?
       w.close unless !w || w.closed?