diff --git a/.gitignore b/.gitignore
index 31dfa7af7..4c0d0f11c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -28,6 +28,7 @@ share/python-wheels/
 *.egg
 MANIFEST
 metagpt/tools/schemas/
+examples/data/search_kb/*.json
 
 # PyInstaller
 #  Usually these files are written by a python scripts from a template
diff --git a/metagpt/rag/engines/simple.py b/metagpt/rag/engines/simple.py
index 22351d8fd..469acbacf 100644
--- a/metagpt/rag/engines/simple.py
+++ b/metagpt/rag/engines/simple.py
@@ -171,6 +171,6 @@ class SimpleEngine(RetrieverQueryEngine):
     def _try_reconstruct_obj(nodes: list[NodeWithScore]):
         """If node is object, then dynamically reconstruct object, and save object to node.metadata["obj"]."""
         for node in nodes:
-            if node.metadata.get("is_obj"):
+            if node.metadata.get("is_obj", False):
                 obj_cls = import_class(node.metadata["obj_cls_name"], node.metadata["obj_mod_name"])
                 node.metadata["obj"] = obj_cls(**node.metadata["obj_dict"])
diff --git a/tests/metagpt/rag/engines/test_simple.py b/tests/metagpt/rag/engines/test_simple.py
index 60e72e422..fd34b4e8d 100644
--- a/tests/metagpt/rag/engines/test_simple.py
+++ b/tests/metagpt/rag/engines/test_simple.py
@@ -97,8 +97,7 @@ class TestSimpleEngine:
         mock_super_aretrieve = mocker.patch(
             "metagpt.rag.engines.simple.RetrieverQueryEngine.aretrieve", new_callable=mocker.AsyncMock
         )
-        nodes = [NodeWithScore(node=TextNode())]
-        mock_super_aretrieve.return_value = nodes
+        mock_super_aretrieve.return_value = [TextNode(text="node_with_score", metadata={"is_obj": False})]
 
         # Setup
         engine = SimpleEngine(retriever=mocker.MagicMock())
@@ -110,7 +109,7 @@ class TestSimpleEngine:
         # Assertions
         mock_query_bundle.assert_called_once_with(test_query)
         mock_super_aretrieve.assert_called_once_with("query_bundle")
-        assert result == nodes
+        assert result[0].text == "node_with_score"
 
     def test_add_docs(self, mocker):
         # Mock
@@ -158,4 +157,4 @@ class TestSimpleEngine:
         assert mock_retriever.add_nodes.call_count == 1
         for node in mock_retriever.add_nodes.call_args[0][0]:
             assert isinstance(node, TextNode)
-            assert "obj_dict" in node.metadata
+            assert "is_obj" in node.metadata