diff --git a/agent/canvas.py b/agent/canvas.py
index fa78762fb..d5c0c0513 100644
--- a/agent/canvas.py
+++ b/agent/canvas.py
@@ -265,7 +265,7 @@ class Canvas:
                 pid = cpn["parent_id"]
                 _, o = cpn["obj"].output(allow_partial=False)
                 _, oo = self.components[pid]["obj"].output(allow_partial=False)
-                self.components[pid]["obj"].set_output(pd.concat([oo.dropna(axis=1), o.dropna(axis=1)], ignore_index=True))
+                self.components[pid]["obj"].set_output(pd.concat([oo.dropna(axis=1), o.dropna(axis=1)], ignore_index=True).dropna())
                 downstream = [pid]
 
             for m in prepare2run(downstream):
diff --git a/agent/component/retrieval.py b/agent/component/retrieval.py
index 5df3335ec..a6f4048d9 100644
--- a/agent/component/retrieval.py
+++ b/agent/component/retrieval.py
@@ -82,7 +82,7 @@ class Retrieval(ComponentBase, ABC):
                                         rank_feature=label_question(query, kbs))
         else:
             kbinfos = {"chunks": [], "doc_aggs": []}
-            
+
         if self._param.use_kg and kbs:
             ck = settings.kg_retrievaler.retrieval(query,
                                                    [kbs[0].tenant_id],