diff --git a/polymorphic/base.py b/polymorphic/base.py
index a407285..83cb7a4 100644
--- a/polymorphic/base.py
+++ b/polymorphic/base.py
@@ -77,15 +77,17 @@ class PolymorphicModelBase(ModelBase):
         for source_name, mgr_name, manager in inherited_managers:
             #print '** add inherited manager from model %s, manager %s, %s' % (source_name, mgr_name, manager.__class__.__name__)
             new_manager = manager._copy_to_model(new_class)
-            new_class.add_to_class(mgr_name, new_manager)
+            if mgr_name == '_default_manager':
+                new_class._default_manager = new_manager
+            else:
+                new_class.add_to_class(mgr_name, new_manager)
 
         # get first user defined manager; if there is one, make it the _default_manager
         # this value is used by the related objects, restoring access to custom queryset methods on related objects.
         user_manager = self.get_first_user_defined_manager(new_class)
         if user_manager:
-            def_mgr = user_manager._copy_to_model(new_class)
             #print '## add default manager', type(def_mgr)
-            new_class.add_to_class('_default_manager', def_mgr)
+            new_class._default_manager = user_manager._copy_to_model(new_class)
             new_class._default_manager._inherited = False   # the default mgr was defined by the user, not inherited
 
         # validate resulting default manager
diff --git a/polymorphic/tests.py b/polymorphic/tests.py
index 64968ed..1a28bcd 100644
--- a/polymorphic/tests.py
+++ b/polymorphic/tests.py
@@ -506,6 +506,29 @@ class PolymorphicTests(TestCase):
         self.assertEqual(show_base_manager(One2OneRelatingModelDerived), "<class 'django.db.models.manager.Manager'> <class 'polymorphic.tests.One2OneRelatingModelDerived'>")
 
 
+    def test_instance_default_manager(self):
+        def show_default_manager(instance):
+            return "{0} {1}".format(
+                repr(type(instance._default_manager)),
+                repr(instance._default_manager.model)
+            )
+
+        plain_a = PlainA(field1='C1')
+        plain_b = PlainB(field2='C1')
+        plain_c = PlainC(field3='C1')
+
+        model_2a = Model2A(field1='C1')
+        model_2b = Model2B(field2='C1')
+        model_2c = Model2C(field3='C1')
+
+        self.assertEqual(show_default_manager(plain_a), "<class 'django.db.models.manager.Manager'> <class 'polymorphic.tests.PlainA'>")
+        self.assertEqual(show_default_manager(plain_b), "<class 'django.db.models.manager.Manager'> <class 'polymorphic.tests.PlainB'>")
+        self.assertEqual(show_default_manager(plain_c), "<class 'django.db.models.manager.Manager'> <class 'polymorphic.tests.PlainC'>")
+
+        self.assertEqual(show_default_manager(model_2a), "<class 'polymorphic.manager.PolymorphicManager'> <class 'polymorphic.tests.Model2A'>")
+        self.assertEqual(show_default_manager(model_2b), "<class 'polymorphic.manager.PolymorphicManager'> <class 'polymorphic.tests.Model2B'>")
+        self.assertEqual(show_default_manager(model_2c), "<class 'polymorphic.manager.PolymorphicManager'> <class 'polymorphic.tests.Model2C'>")
+
     def test_foreignkey_field(self):
         self.create_model2abcd()