diff --git a/api/core/app/apps/pipeline/pipeline_runner.py b/api/core/app/apps/pipeline/pipeline_runner.py
index 57cc1c316c..12506049aa 100644
--- a/api/core/app/apps/pipeline/pipeline_runner.py
+++ b/api/core/app/apps/pipeline/pipeline_runner.py
@@ -176,6 +176,7 @@ class PipelineRunner(WorkflowBasedAppRunner):
             invoke_from=self.application_generate_entity.invoke_from,
             call_depth=self.application_generate_entity.call_depth,
             graph_runtime_state=graph_runtime_state,
+            variable_pool=variable_pool,
         )
 
         generator = workflow_entry.run()
diff --git a/api/models/workflow.py b/api/models/workflow.py
index 21577050d0..f654679956 100644
--- a/api/models/workflow.py
+++ b/api/models/workflow.py
@@ -368,7 +368,7 @@ class Workflow(Base):
         if not tenant_id:
             return []
 
-        environment_variables_dict: dict[str, Any] = json.loads(self._environment_variables)
+        environment_variables_dict: dict[str, Any] = json.loads(self._environment_variables or "{}")
         results = [
             variable_factory.build_environment_variable_from_mapping(v) for v in environment_variables_dict.values()
         ]