diff --git a/proteus/config.py b/proteus/config.py
index f8bc7b01aa..2eccfff55c 100644
--- a/proteus/config.py
+++ b/proteus/config.py
@@ -154,7 +154,7 @@ class TrytondConfig(Config):
 
     def __eq__(self, other):
         if not isinstance(other, TrytondConfig):
-            raise NotImplemented
+            raise NotImplementedError
         return (self.database_name == other.database_name
             and self._user == other._user
             and self.database_type == other.database_type
@@ -211,7 +211,7 @@ class XmlrpcConfig(Config):
 
     def __eq__(self, other):
         if not isinstance(other, XmlrpcConfig):
-            raise NotImplemented
+            raise NotImplementedError
         return self.url == other.url
 
     def __hash__(self):
diff --git a/proteus/tests/test_config.py b/proteus/tests/test_config.py
index 8c568b49dd..35433a38c1 100644
--- a/proteus/tests/test_config.py
+++ b/proteus/tests/test_config.py
@@ -26,4 +26,4 @@ class TestConfig(TestCase):
         config2 = proteus.config.get_config()
         self.assertEqual(config1, config2)
 
-        self.assertEqual(config1.__eq__(None), NotImplemented)
+        self.assertRaises(NotImplementedError, config1.__eq__, None)