diff --git a/tox.ini b/tox.ini
index b1061a57c6a136cb29f77a1d0c03383ab82ecf8b..0d245e03ef9c8fe2151e173cd1a10964d47ef82b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,3 +9,6 @@ deps = .
     pytest-cov
     jsonschema==4.0.1
 commands=py.test --cov=caosdb -vv {posargs}
+
+[flake8]
+max-line-length=100