diff --git a/app/models/__init__.py b/app/models/__init__.py
index c42bb028a..791c4a0c8 100644
--- a/app/models/__init__.py
+++ b/app/models/__init__.py
@@ -13,7 +13,7 @@ class JSONModel(SerialisedModel):
         # in the case of a bad request _dict may be `None`
         self._dict = _dict or {}
         for property in self.ALLOWED_PROPERTIES:
-            if property in self._dict and not hasattr(self, property):
+            if property in self._dict:
                 setattr(self, property, self._dict[property])
 
     def __bool__(self):
diff --git a/app/models/job.py b/app/models/job.py
index e08a8a87a..65679f3aa 100644
--- a/app/models/job.py
+++ b/app/models/job.py
@@ -28,7 +28,6 @@ class Job(JSONModel):
         'template_version',
         'original_file_name',
         'created_at',
-        'processing_started',
         'notification_count',
         'created_by',
         'template_type',
diff --git a/tests/app/models/test_base_model.py b/tests/app/models/test_base_model.py
index 48500b0c7..5ccabc850 100644
--- a/tests/app/models/test_base_model.py
+++ b/tests/app/models/test_base_model.py
@@ -11,7 +11,7 @@ def test_looks_up_from_dict():
     assert Custom({'foo': 'bar'}).foo == 'bar'
 
 
-def test_prefers_property_to_dict():
+def test_raises_when_overriding_custom_properties():
 
     class Custom(JSONModel):
 
@@ -19,9 +19,12 @@ def test_prefers_property_to_dict():
 
         @property
         def foo(self):
-            return 'bar'
+            pass
 
-    assert Custom({'foo': 'NOPE'}).foo == 'bar'
+    with pytest.raises(AttributeError) as e:
+        Custom({'foo': 'NOPE'})
+
+    assert str(e.value) == "can't set attribute"
 
 
 @pytest.mark.parametrize('json_response', (