diff --git a/requirements.txt b/requirements.txt
index a340af3..7254a8d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
+flake8 >= 4.0.0
 python-subunit >= 0.0.18
 testtools >= 0.9.30
 dpkt >= 1.8.8  # BSD