diff --git a/egs/librispeech/ASR/pruned_transducer_stateless7/optim.py b/egs/librispeech/ASR/pruned_transducer_stateless7/optim.py
index 776c88a0e..ea9f82bb8 100644
--- a/egs/librispeech/ASR/pruned_transducer_stateless7/optim.py
+++ b/egs/librispeech/ASR/pruned_transducer_stateless7/optim.py
@@ -22,7 +22,6 @@ from typing import Dict, List, Optional, Tuple, Union
 
 import torch
 from lhotse.utils import fix_random_seed
-from scaling import ActivationBalancer
 from torch import Tensor
 from torch.optim import Optimizer