diff --git a/egs/librispeech/ASR/zipformer/optim.py b/egs/librispeech/ASR/zipformer/optim.py
index 891a4177f..a663db708 100644
--- a/egs/librispeech/ASR/zipformer/optim.py
+++ b/egs/librispeech/ASR/zipformer/optim.py
@@ -22,8 +22,7 @@ from typing import Dict, List, Optional, Tuple, Union
 
 import torch
 from lhotse.utils import fix_random_seed
-from torch import Tensor
-from torch import nn
+from torch import Tensor, nn
 from torch.optim import Optimizer