diff --git a/expo/MCTS.py b/expo/MCTS.py
index 8778554ed..2ce559ae0 100644
--- a/expo/MCTS.py
+++ b/expo/MCTS.py
@@ -43,6 +43,8 @@ def create_initial_state(task, start_task_id, data_config, args):
         task = get_mle_task_id(args.custom_dataset_dir)
     else:
         dataset_config = data_config["datasets"][task]
+        if dataset_config["metric"] == "rmse":
+            args.low_is_better = True
         datasets_dir = get_split_dataset_path(task, data_config)
         requirement = generate_task_requirement(
             task, data_config, is_di=True, special_instruction=args.special_instruction