diff --git a/src/transformers/configuration_transfo_xl.py b/src/transformers/configuration_transfo_xl.py
index e0e2682e133..9214449637e 100644
--- a/src/transformers/configuration_transfo_xl.py
+++ b/src/transformers/configuration_transfo_xl.py
@@ -17,6 +17,7 @@
 
 
 import warnings
+
 from .configuration_utils import PretrainedConfig
 from .utils import logging