diff --git a/api/services/async_workflow_service.py b/api/services/async_workflow_service.py
index f54f41a48a..034d7ffedb 100644
--- a/api/services/async_workflow_service.py
+++ b/api/services/async_workflow_service.py
@@ -111,7 +111,9 @@ class AsyncWorkflowService:
             app_id=trigger_data.app_id,
             workflow_id=workflow.id,
             root_node_id=trigger_data.root_node_id,
-            trigger_metadata=trigger_data.trigger_metadata.model_dump_json(),
+            trigger_metadata=(
+                trigger_data.trigger_metadata.model_dump_json() if trigger_data.trigger_metadata else "{}"
+            ),
             trigger_type=trigger_data.trigger_type,
             trigger_data=trigger_data.model_dump_json(),
             inputs=json.dumps(dict(trigger_data.inputs)),