diff --git a/src/llmtuner/tuner/sft/trainer.py b/src/llmtuner/tuner/sft/trainer.py
index 38b94669..7a20e9b4 100644
--- a/src/llmtuner/tuner/sft/trainer.py
+++ b/src/llmtuner/tuner/sft/trainer.py
@@ -33,10 +33,10 @@ class CustomSeq2SeqTrainer(Seq2SeqTrainer):
 
         Subclass and override to inject custom behavior.
         """
+        labels = inputs["labels"].clone() if "labels" in inputs else None # backup labels
         if self.args.predict_with_generate:
             assert self.tokenizer.padding_side == "left", "This method only accepts left-padded tensor."
             prompt_len, label_len = inputs["input_ids"].size(-1), inputs["labels"].size(-1)
-            labels = inputs["labels"].clone()
             if prompt_len > label_len:
                 inputs["labels"] = self._pad_tensors_to_target_len(inputs["labels"], inputs["input_ids"])
             if label_len > prompt_len: