diff --git a/cassandra/cqlengine/columns.py b/cassandra/cqlengine/columns.py
index 80b2e5c4..9e7c2cad 100644
--- a/cassandra/cqlengine/columns.py
+++ b/cassandra/cqlengine/columns.py
@@ -235,8 +235,6 @@ class Column(object):
         """
         Converts python value into database value
         """
-        if value is None and self.has_default:
-            return self.get_default()
         return value
 
     @property
@@ -948,7 +946,16 @@ class Map(BaseContainerColumn):
 class UDTValueManager(BaseValueManager):
     @property
     def changed(self):
-        return self.value != self.previous_value or (self.value is not None and self.value.has_changed_fields())
+        if self.explicit:
+            return self.value != self.previous_value
+
+        default_value = self.column.get_default()
+        if not self.column._val_is_null(default_value):
+            return self.value != default_value
+        elif self.previous_value is None:
+            return not self.column._val_is_null(self.value) and self.value.has_changed_fields()
+
+        return False
 
     def reset_previous_value(self):
         if self.value is not None:
diff --git a/tests/integration/cqlengine/model/test_updates.py b/tests/integration/cqlengine/model/test_updates.py
index c22668bc..2f966e7e 100644
--- a/tests/integration/cqlengine/model/test_updates.py
+++ b/tests/integration/cqlengine/model/test_updates.py
@@ -183,9 +183,11 @@ class ModelWithDefaultTests(BaseCassEngTestCase):
 
     def setUp(self):
         sync_table(ModelWithDefault)
+        sync_table(ModelWithDefaultCollection)
 
     def tearDown(self):
         drop_table(ModelWithDefault)
+        drop_table(ModelWithDefaultCollection)
 
     def test_value_override_with_default(self):
         """
@@ -309,28 +311,35 @@ class ModelWithDefaultTests(BaseCassEngTestCase):
         udt, udt_default = UDT(age=1, mf={6: 6}), UDT(age=1, mf={6: 6})
 
         item = ModelWithDefaultCollection.create(id=1, mf={1: 1}, dummy=1, udt=udt, udt_default=udt_default).save()
-        self.assertEqual(ModelWithDefaultCollection.all().get()._as_dict(),
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=1)._as_dict(),
                          {'id': 1, 'dummy': 1, 'mf': {1: 1}, "udt": udt, "udt_default": udt_default})
 
         udt, udt_default = UDT(age=1, mf={5: 5}), UDT(age=1, mf={5: 5})
         item.update(mf={2: 2}, udt=udt, udt_default=udt_default)
-        self.assertEqual(ModelWithDefaultCollection.all().get()._as_dict(),
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=1)._as_dict(),
                          {'id': 1, 'dummy': 1, 'mf': {2: 2}, "udt": udt, "udt_default": udt_default})
 
         udt, udt_default = UDT(age=1, mf=None), UDT(age=1, mf=None)
         expected_udt, expected_udt_default = UDT(age=1, mf={}), UDT(age=1, mf={})
         item.update(mf=None, udt=udt, udt_default=udt_default)
-        self.assertEqual(ModelWithDefaultCollection.all().get()._as_dict(),
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=1)._as_dict(),
                          {'id': 1, 'dummy': 1, 'mf': {}, "udt": expected_udt, "udt_default": expected_udt_default})
 
-        udt_default = UDT(age=1, mf=None), UDT(age=1, mf={5:5})
-        item = ModelWithDefaultCollection.create(id=2, dummy=2).save()
-        self.assertEqual(ModelWithDefaultCollection.all().get(id=2)._as_dict(),
+        udt_default = UDT(age=1, mf={2:2}, dummy_udt=42)
+        item = ModelWithDefaultCollection.create(id=2, dummy=2)
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=2)._as_dict(),
                          {'id': 2, 'dummy': 2, 'mf': {2: 2}, "udt": None, "udt_default": udt_default})
 
         udt, udt_default = UDT(age=1, mf={1: 1, 6: 6}), UDT(age=1, mf={1: 1, 6: 6})
         item.update(mf={1: 1, 4: 4}, udt=udt, udt_default=udt_default)
-        self.assertEqual(ModelWithDefaultCollection.all().get(id=2)._as_dict(),
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=2)._as_dict(),
                          {'id': 2, 'dummy': 2, 'mf': {1: 1, 4: 4}, "udt": udt, "udt_default": udt_default})
 
-        drop_table(ModelWithDefaultCollection)
+        item.update(udt_default=None)
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=2)._as_dict(),
+                         {'id': 2, 'dummy': 2, 'mf': {1: 1, 4: 4}, "udt": udt, "udt_default": None})
+
+        udt_default = UDT(age=1, mf={2:2})
+        item.update(udt_default=udt_default)
+        self.assertEqual(ModelWithDefaultCollection.objects.get(id=2)._as_dict(),
+                         {'id': 2, 'dummy': 2, 'mf': {1: 1, 4: 4}, "udt": udt, "udt_default": udt_default})