diff --git a/qlib/contrib/online/operator.py b/qlib/contrib/online/operator.py
index c8b44f578..d2307dad5 100644
--- a/qlib/contrib/online/operator.py
+++ b/qlib/contrib/online/operator.py
@@ -148,7 +148,7 @@ class Operator:
         for user_id, user in um.users.items():
             dates, trade_exchange = prepare(um, trade_date, user_id, exchange_config)
             executor = SimulatorExecutor(trade_exchange=trade_exchange)
-            if not str(dates[0].date()) == str(pred_date.date()):
+            if str(dates[0].date()) != str(pred_date.date()):
                 raise ValueError(
                     "The account data is not newest! last trading date {}, today {}".format(
                         dates[0].date(), trade_date.date()