diff --git a/src/memos/api/routers/server_router.py b/src/memos/api/routers/server_router.py
index d2392f927..86e7a300a 100644
--- a/src/memos/api/routers/server_router.py
+++ b/src/memos/api/routers/server_router.py
@@ -332,6 +332,7 @@ def search_memories(search_req: APISearchRequest):
         "text_mem": [],
         "act_mem": [],
         "para_mem": [],
+        "pref_mem": "",
     }
 
     search_mode = search_req.mode