diff --git a/openrlhf/trainer/ppo_utils/experience_maker.py b/openrlhf/trainer/ppo_utils/experience_maker.py
index 798eabc52..347176707 100644
--- a/openrlhf/trainer/ppo_utils/experience_maker.py
+++ b/openrlhf/trainer/ppo_utils/experience_maker.py
@@ -369,11 +369,11 @@ def _generate_vllm(self, prompts: List[str], **kwargs) -> Tuple[torch.Tensor, to
         for output in outputs:
             # left padding input
             input_len = len(output.prompt_token_ids)
-            input_ids = [pad_token_id] * (max_input_len - input_len) + list(output.prompt_token_ids)
+            input_ids = [pad_token_id] * (max_input_len - input_len) + output.prompt_token_ids
 
             # right padding output
             output_len = len(output.outputs[0].token_ids)
-            output_ids = list(output.outputs[0].token_ids) + [pad_token_id] * (max_output_len - output_len)
+            output_ids = output.outputs[0].token_ids + [pad_token_id] * (max_output_len - output_len)
 
             if output_ids[output_len - 1] != eos_token_id:
                 output_ids[min(output_len, len(output_ids) - 1)] = eos_token_id