diff --git a/lib/mongo_mapper/document.rb b/lib/mongo_mapper/document.rb
index bc346f7fa..60d4e9857 100644
--- a/lib/mongo_mapper/document.rb
+++ b/lib/mongo_mapper/document.rb
@@ -36,7 +36,6 @@ def self.included(model)
 
     module ClassMethods
       def inherited(subclass)
-        key :_type, String unless keys.keys.include?(:_type)
         subclass.set_collection_name(collection_name)
         super
       end
diff --git a/lib/mongo_mapper/plugins/keys.rb b/lib/mongo_mapper/plugins/keys.rb
index 542f896b5..b9a186dac 100644
--- a/lib/mongo_mapper/plugins/keys.rb
+++ b/lib/mongo_mapper/plugins/keys.rb
@@ -7,6 +7,7 @@ def self.configure(model)
 
       module ClassMethods
         def inherited(descendant)
+          key :_type, String unless keys.keys.include?(:_type)
           descendant.instance_variable_set(:@keys, keys.dup)
           super
         end
diff --git a/test/unit/test_embedded_document.rb b/test/unit/test_embedded_document.rb
index d8032fae1..c9026e5f7 100644
--- a/test/unit/test_embedded_document.rb
+++ b/test/unit/test_embedded_document.rb
@@ -179,17 +179,17 @@ class ::OtherChild < ::Parent
 
       context "keys" do
         should "be inherited" do
-          Grandparent.keys.keys.sort.should == ['_id', 'grandparent']
-          Parent.keys.keys.sort.should == ['_id', 'grandparent', 'parent']
-          Child.keys.keys.sort.should  == ['_id', 'child', 'grandparent', 'parent']
+          Grandparent.keys.keys.sort.should == ['_id', '_type', 'grandparent']
+          Parent.keys.keys.sort.should == ['_id', '_type', 'grandparent', 'parent']
+          Child.keys.keys.sort.should  == ['_id', '_type', 'child', 'grandparent', 'parent']
         end
 
         should "propogate to descendants if key added after class definition" do
-          Grandparent.key :_type, String
+          Grandparent.key :foo, String
 
-          Grandparent.keys.keys.sort.should == ['_id', '_type', 'grandparent']
-          Parent.keys.keys.sort.should      == ['_id', '_type', 'grandparent', 'parent']
-          Child.keys.keys.sort.should       == ['_id', '_type', 'child', 'grandparent', 'parent']
+          Grandparent.keys.keys.sort.should == ['_id', '_type', 'foo', 'grandparent']
+          Parent.keys.keys.sort.should      == ['_id', '_type', 'foo', 'grandparent', 'parent']
+          Child.keys.keys.sort.should       == ['_id', '_type', 'child', 'foo', 'grandparent', 'parent']
         end
 
         should "not add anonymous objects to the ancestor tree" do
diff --git a/test/unit/test_rails_compatibility.rb b/test/unit/test_rails_compatibility.rb
index 24255f135..69be94200 100644
--- a/test/unit/test_rails_compatibility.rb
+++ b/test/unit/test_rails_compatibility.rb
@@ -29,9 +29,9 @@ class SecondItem < Item
     end
     
     should "have column names" do
-      Item.column_names.sort.should == ['_id', 'for_all']
-      FirstItem.column_names.sort.should == ['_id', 'first_only', 'for_all']
-      SecondItem.column_names.sort.should == ['_id', 'for_all', 'second_only']
+      Item.column_names.sort.should == ['_id', '_type', 'for_all']
+      FirstItem.column_names.sort.should == ['_id', '_type', 'first_only', 'for_all']
+      SecondItem.column_names.sort.should == ['_id', '_type', 'for_all', 'second_only']
     end
     
     should "alias new to new_record?" do