diff --git a/cinder/tests/unit/volume/flows/test_create_volume_flow.py b/cinder/tests/unit/volume/flows/test_create_volume_flow.py
index 2a7b625bc95..5b4ddb35f3e 100644
--- a/cinder/tests/unit/volume/flows/test_create_volume_flow.py
+++ b/cinder/tests/unit/volume/flows/test_create_volume_flow.py
@@ -667,8 +667,10 @@ class CreateVolumeFlowTestCase(test.TestCase):
         fake_key_manager = mock_key_manager.MockKeyManager()
         volume_type = {'name': 'type1', 'id': 1}
 
-        with mock.patch.object(fake_key_manager, 'create_key',
-                               side_effect=castellan_exc.KeyManagerError):
+        with mock.patch.object(
+            fake_key_manager, 'create_key',
+            side_effect=castellan_exc.KeyManagerError('foo')
+        ):
             with mock.patch.object(fake_key_manager, 'get',
                                    return_value=fakes.ENCRYPTION_KEY_ID):