diff --git a/ChangeLog b/ChangeLog
index 5838a5cc80..07893ce708 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Oct  3 21:19:18 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm_method.c (rb_add_method_def): no redefinition warning on
+	  undef.
+
 Sat Oct  3 18:51:11 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* object.c (rb_f_integer): now Integer() takes optional base
diff --git a/test/ruby/test_class.rb b/test/ruby/test_class.rb
index 409fc49e4e..8fe1272314 100644
--- a/test/ruby/test_class.rb
+++ b/test/ruby/test_class.rb
@@ -150,7 +150,15 @@ class TestClass < Test::Unit::TestCase
       Class.new do
         define_method(:foo) do end
         alias bar foo
-        alias barf oo
+        alias bar foo
+      end
+    end
+    assert_equal("", stderr)
+
+    stderr = EnvUtil.verbose_warning do
+      Class.new do
+        def foo; end
+        undef foo
       end
     end
     assert_equal("", stderr)
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index c50cd38b79..59c965325f 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -845,5 +845,13 @@ class TestModule < Test::Unit::TestCase
       end
     end
     assert_equal("", stderr, '[ruby-dev:39397]')
+
+    stderr = EnvUtil.verbose_warning do
+      Module.new do
+        def foo; end
+        undef foo
+      end
+    end
+    assert_equal("", stderr)
   end
 end
diff --git a/vm_method.c b/vm_method.c
index a879d0567f..ec381c40d7 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -185,6 +185,7 @@ rb_add_method_def(VALUE klass, ID mid, rb_method_type_t type, rb_method_definiti
 	rb_vm_check_redefinition_opt_method(old_me);
 
 	if (RTEST(ruby_verbose) &&
+	    type != VM_METHOD_TYPE_UNDEF &&
 	    old_def->alias_count == 0 &&
 	    old_def->type != VM_METHOD_TYPE_UNDEF &&
 	    old_def->type != VM_METHOD_TYPE_ZSUPER) {