diff --git a/.flake8 b/.flake8
index cfacdc5c9..68a40999a 100644
--- a/.flake8
+++ b/.flake8
@@ -8,6 +8,8 @@ per-file-ignores =
     egs/aishell/ASR/*/conformer.py: E501,
     egs/tedlium3/ASR/*/conformer.py: E501,
     egs/tedlium3/ASR/local/display_manifest_statistics.py: E501,
+    # invalid escape sequence (cause by tex formular), W605
+    icefall/utils.py: E501, W605
 
 exclude =
   .git,