diff --git a/activerecord/lib/active_record/xml_serialization.rb b/activerecord/lib/active_record/xml_serialization.rb
index 78a3a2193c..7a8167534d 100644
--- a/activerecord/lib/active_record/xml_serialization.rb
+++ b/activerecord/lib/active_record/xml_serialization.rb
@@ -297,11 +297,11 @@ module ActiveRecord #:nodoc:
           end
         end
     end
-  
+
     class MethodAttribute < Attribute #:nodoc:
       protected
         def compute_type
-          Hash::XML_TYPE_NAMES[@record.send(name).class] || :string
+          Hash::XML_TYPE_NAMES[@record.send(name).class.name] || :string
         end
     end
   end
diff --git a/activerecord/test/base_test.rb b/activerecord/test/base_test.rb
index 055f5e8670..9a67426ba2 100755
--- a/activerecord/test/base_test.rb
+++ b/activerecord/test/base_test.rb
@@ -1340,8 +1340,8 @@ class BasicsTest < Test::Unit::TestCase
 
   def test_array_to_xml_including_methods
     xml = [ topics(:first), topics(:second) ].to_xml(:indent => 0, :skip_instruct => true, :methods => [ :topic_id ])
-    assert xml.include?(%(<topic-id type="integer">#{topics(:first).topic_id}</topic-id>))
-    assert xml.include?(%(<topic-id type="integer">#{topics(:second).topic_id}</topic-id>))
+    assert xml.include?(%(<topic-id type="integer">#{topics(:first).topic_id}</topic-id>)), xml
+    assert xml.include?(%(<topic-id type="integer">#{topics(:second).topic_id}</topic-id>)), xml
   end
   
   def test_array_to_xml_including_has_one_association