diff --git a/mistral/event_engine/default_event_engine.py b/mistral/event_engine/default_event_engine.py
index 85e5ae568..0336623d7 100644
--- a/mistral/event_engine/default_event_engine.py
+++ b/mistral/event_engine/default_event_engine.py
@@ -255,6 +255,7 @@ class DefaultEventEngine(base.EventEngine):
                 self.engine_client.start_workflow(
                     t['workflow_id'],
                     t['workflow_namespace'],
+                    None,
                     t['workflow_input'],
                     description=json.dumps(description),
                     **workflow_params
diff --git a/mistral/tests/unit/services/test_event_engine.py b/mistral/tests/unit/services/test_event_engine.py
index 3181639f7..ba1ebc72d 100644
--- a/mistral/tests/unit/services/test_event_engine.py
+++ b/mistral/tests/unit/services/test_event_engine.py
@@ -140,7 +140,10 @@ class EventEngineTest(base.DbTestCase):
 
             args, kwargs = client_mock.start_workflow.call_args
 
-            self.assertEqual((EVENT_TRIGGER['workflow_id'], '', {}), args)
+            self.assertEqual(
+                (EVENT_TRIGGER['workflow_id'], '', None, {}),
+                args
+            )
             self.assertDictEqual(
                 {
                     'service': 'fake_publisher',
@@ -181,7 +184,10 @@ class EventEngineTest(base.DbTestCase):
 
             args, kwargs = client_mock.start_workflow.call_args
 
-            self.assertEqual((EVENT_TRIGGER['workflow_id'], '', {}), args)
+            self.assertEqual(
+                (EVENT_TRIGGER['workflow_id'], '', None, {}),
+                args
+            )
             self.assertDictEqual(
                 {
                     'service': 'fake_publisher',