diff --git a/python/damask/_config.py b/python/damask/_config.py
index 627fc88c8..9e1686a30 100644
--- a/python/damask/_config.py
+++ b/python/damask/_config.py
@@ -162,11 +162,11 @@ class Config(dict):
     @abc.abstractmethod
     def is_complete(self):
         """Check for completeness."""
-        pass
+        raise NotImplementedError
 
 
     @property
     @abc.abstractmethod
     def is_valid(self):
         """Check for valid file layout."""
-        pass
+        raise NotImplementedError
diff --git a/python/tests/test_Config.py b/python/tests/test_Config.py
index d2f0b5e72..ae93b231d 100644
--- a/python/tests/test_Config.py
+++ b/python/tests/test_Config.py
@@ -49,10 +49,12 @@ class TestConfig:
         assert Config({'A':np.ones(3,'i')}).__repr__() == Config({'A':[1,1,1]}).__repr__()
 
     def test_abstract_is_valid(self):
-        assert Config().is_valid is None
+        with pytest.raises(NotImplementedError):
+            Config().is_valid
 
     def test_abstract_is_complete(self):
-        assert Config().is_complete is None
+        with pytest.raises(NotImplementedError):
+            Config().is_complete
 
     @pytest.mark.parametrize('data',[Rotation.from_random(),Orientation.from_random(lattice='cI')])
     def test_rotation_orientation(self,data):