diff --git a/backend/app/tools.py b/backend/app/tools.py
index 9c701f41..14458866 100644
--- a/backend/app/tools.py
+++ b/backend/app/tools.py
@@ -191,7 +191,7 @@ class Retrieval(BaseTool):
 
 def get_retriever(assistant_id: str, thread_id: str):
     return vstore.as_retriever(
-        search_kwargs={"filter": {"namespace": {"in": [assistant_id, thread_id]}}}
+        search_kwargs={"filter": {"namespace": {"$in": [assistant_id, thread_id]}}}
     )