diff --git a/api/controllers/web/app.py b/api/controllers/web/app.py
index 07ce098298..fb2a3676d8 100644
--- a/api/controllers/web/app.py
+++ b/api/controllers/web/app.py
@@ -51,7 +51,7 @@ class AppParameterApi(WebApiResource):
                 raise AppUnavailableError()
 
             features_dict = workflow.features_dict
-            user_input_form = workflow.user_input_form
+            user_input_form = workflow.user_input_form()
         else:
             app_model_config = app_model.app_model_config
             features_dict = app_model_config.to_dict()
diff --git a/api/models/model.py b/api/models/model.py
index 84599e930b..af8057077c 100644
--- a/api/models/model.py
+++ b/api/models/model.py
@@ -91,7 +91,7 @@ class App(db.Model):
     @property
     def workflow(self):
         if self.workflow_id:
-            from api.models.workflow import Workflow
+            from .workflow import Workflow
             return db.session.query(Workflow).filter(Workflow.id == self.workflow_id).first()
 
         return None
diff --git a/api/models/workflow.py b/api/models/workflow.py
index dccb69498d..e14274d609 100644
--- a/api/models/workflow.py
+++ b/api/models/workflow.py
@@ -127,7 +127,7 @@ class Workflow(db.Model):
 
     @property
     def features_dict(self):
-        return json.loads(self.features) if self.features else None
+        return json.loads(self.features) if self.features else {}
 
     def user_input_form(self) -> list:
         # get start node from graph