diff --git a/tox.ini b/tox.ini
index 4dcb8348..32fc8756 100644
--- a/tox.ini
+++ b/tox.ini
@@ -14,5 +14,5 @@ commands =
 
 [pep8]
 exclude = pbr-*,.venv,.tox,.git,doc,dist,tools,vcsversion.py,.pyc,ryu/contrib,dictconfig.py
-ignore = E113,E116,E402,E711,E731,E501
+ignore = E113,E116,E402,E711,E731,E501,W503