diff --git a/src/llmtuner/hparams/finetuning_args.py b/src/llmtuner/hparams/finetuning_args.py
index 6fe951f1..0dd28a8f 100644
--- a/src/llmtuner/hparams/finetuning_args.py
+++ b/src/llmtuner/hparams/finetuning_args.py
@@ -102,7 +102,7 @@ class RLHFArguments:
         default="sigmoid",
         metadata={"help": "The type of DPO loss to use."},
     )
-    dpo_label_smoothing = field(
+    dpo_label_smoothing: float = field(
         default=0.0,
         metadata={"help": "The robust DPO label smoothing parameter in cDPO that should be between 0 and 0.5."},
     )