diff --git a/activerecord/lib/active_record/attributes/typecasting.rb b/activerecord/lib/active_record/attributes/typecasting.rb
index de36a297eb..56c32f9895 100644
--- a/activerecord/lib/active_record/attributes/typecasting.rb
+++ b/activerecord/lib/active_record/attributes/typecasting.rb
@@ -37,6 +37,12 @@ module ActiveRecord
         hash.merge!(self)
         hash
       end
+      
+      def dup # :nodoc:
+        copy = super
+        copy.types = types.dup
+        copy
+      end
 
       # Provides a duplicate with typecasting disabled.
       #
diff --git a/activerecord/test/cases/attributes/typecasting_test.rb b/activerecord/test/cases/attributes/typecasting_test.rb
index c712f224b2..8a3b551375 100644
--- a/activerecord/test/cases/attributes/typecasting_test.rb
+++ b/activerecord/test/cases/attributes/typecasting_test.rb
@@ -86,12 +86,14 @@ class TypecastingTest < ActiveRecord::TestCase
   end
 
   test "without typecasting" do
+    @attributes.merge!('comments_count' => '5')
     attributes = @attributes.without_typecast
-    attributes['comments_count'] = '5'
-
+    
     assert_equal '5', attributes['comments_count']
+    assert_equal  5,  @attributes['comments_count'], "Original attributes should typecast"
   end
 
+
   test "typecast all attributes" do
     attributes = @attributes.merge('title' => 'I love sandwiches', 'comments_count' => '5')
     attributes.typecast!