diff --git a/castellan/tests/unit/key_manager/mock_key_manager.py b/castellan/tests/unit/key_manager/mock_key_manager.py
index ab463834..688e9492 100644
--- a/castellan/tests/unit/key_manager/mock_key_manager.py
+++ b/castellan/tests/unit/key_manager/mock_key_manager.py
@@ -178,7 +178,11 @@ class MockKeyManager(key_manager.KeyManager):
         if context is None:
             raise exception.Forbidden()
 
-        obj = copy.deepcopy(self.keys[managed_object_id])
+        try:
+            obj = copy.deepcopy(self.keys[managed_object_id])
+        except KeyError:
+            raise exception.ManagedObjectNotFoundError()
+
         if metadata_only:
             if hasattr(obj, "_key"):
                 obj._key = None
@@ -197,7 +201,10 @@ class MockKeyManager(key_manager.KeyManager):
         if context is None:
             raise exception.Forbidden()
 
-        del self.keys[managed_object_id]
+        try:
+            del self.keys[managed_object_id]
+        except KeyError:
+            raise exception.ManagedObjectNotFoundError()
 
     def add_consumer(self, context, managed_object_id, consumer_data):
         if context is None:
diff --git a/castellan/tests/unit/key_manager/test_mock_key_manager.py b/castellan/tests/unit/key_manager/test_mock_key_manager.py
index d03e756f..a79232ca 100644
--- a/castellan/tests/unit/key_manager/test_mock_key_manager.py
+++ b/castellan/tests/unit/key_manager/test_mock_key_manager.py
@@ -201,22 +201,26 @@ class MockKeyManagerTestCase(test_key_mgr.KeyManagerTestCase):
                           self.key_mgr.get, None, None)
 
     def test_get_unknown_key(self):
-        self.assertRaises(KeyError, self.key_mgr.get, self.context, None)
+        self.assertRaises(
+            exception.ManagedObjectNotFoundError, self.key_mgr.get,
+            self.context, None)
 
     def test_delete_key(self):
         key_id = self.key_mgr.create_key(self.context)
         self.key_mgr.delete(self.context, key_id)
 
-        self.assertRaises(KeyError, self.key_mgr.get, self.context,
-                          key_id)
+        self.assertRaises(
+            exception.ManagedObjectNotFoundError, self.key_mgr.get,
+            self.context, key_id)
 
     def test_delete_null_context(self):
         self.assertRaises(exception.Forbidden,
                           self.key_mgr.delete, None, None)
 
     def test_delete_unknown_key(self):
-        self.assertRaises(KeyError, self.key_mgr.delete, self.context,
-                          None)
+        self.assertRaises(
+            exception.ManagedObjectNotFoundError, self.key_mgr.delete,
+            self.context, None)
 
     def test_list_null_context(self):
         self.assertRaises(exception.Forbidden, self.key_mgr.list, None)