diff --git a/sotopia-chat/chat_server.py b/sotopia-chat/chat_server.py
index 21eba5eff..e6134e908 100644
--- a/sotopia-chat/chat_server.py
+++ b/sotopia-chat/chat_server.py
@@ -222,8 +222,10 @@ async def _assign_left_or_right_and_run(session_id: str) -> None:
         case 2:
             if await r.llen("chat_server_combos_double") == 0:
                 await gather(
-                    _assign_left_or_right_and_run(session_id)
-                    for session_id in session_ids
+                    *[
+                        _assign_left_or_right_and_run(session_id)
+                        for session_id in session_ids
+                    ]
                 )
             else:
                 agent_env_combo_pk: str = (