diff --git a/backend/open_webui/routers/retrieval.py b/backend/open_webui/routers/retrieval.py
index e4bab5289..baabaf2c9 100644
--- a/backend/open_webui/routers/retrieval.py
+++ b/backend/open_webui/routers/retrieval.py
@@ -760,7 +760,11 @@ def save_docs_to_vector_db(
     # for meta-data so convert them to string.
     for metadata in metadatas:
         for key, value in metadata.items():
-            if isinstance(value, datetime):
+            if (
+                isinstance(value, datetime)
+                or isinstance(value, list)
+                or isinstance(value, dict)
+            ):
                 metadata[key] = str(value)
 
     try: