diff --git a/ChangeLog b/ChangeLog
index 573002ad94..58f54dc968 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Jun 28 02:43:35 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* class.c (rb_mod_init_copy): when class is dup'ed, a metaclass of the
+	  class should be attached to the dup'ed class, not the original
+	  class.  [ruby-core:30843] [Bug #3461]
+
 Sun Jun 27 23:31:17 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* include/ruby/io.h, io.c: reverted r21709.
diff --git a/class.c b/class.c
index 7747a4e4d5..7cc7551b62 100644
--- a/class.c
+++ b/class.c
@@ -146,6 +146,7 @@ rb_mod_init_copy(VALUE clone, VALUE orig)
     rb_obj_init_copy(clone, orig);
     if (!FL_TEST(CLASS_OF(clone), FL_SINGLETON)) {
 	RBASIC(clone)->klass = rb_singleton_class_clone(orig);
+	rb_singleton_class_attached(RBASIC(clone)->klass, (VALUE)clone);
     }
     RCLASS_SUPER(clone) = RCLASS_SUPER(orig);
     if (RCLASS_IV_TBL(orig)) {