diff --git a/tests/requirements.txt b/tests/requirements.txt
index 081c409..da1843c 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,3 +1,5 @@
+# To avoid https://github.com/tholo/pytest-flake8/issues/87
+flake8 <5.0.0
 pytest
 pytest-cov
 pytest-doctestplus