diff --git a/api/apps/sdk/session.py b/api/apps/sdk/session.py
index 1716db9ee..74e770899 100644
--- a/api/apps/sdk/session.py
+++ b/api/apps/sdk/session.py
@@ -466,6 +466,8 @@ def list_session(tenant_id, chat_id):
             message_num = 0
             while message_num < len(messages) and message_num < len(conv["reference"]):
                 if message_num != 0 and messages[message_num]["role"] != "user":
+                    if message_num >= len(conv["reference"]):
+                        break
                     chunk_list = []
                     if "chunks" in conv["reference"][message_num]:
                         chunks = conv["reference"][message_num]["chunks"]