diff --git a/tox.ini b/tox.ini
index 94d4f8e..748c0ea 100644
--- a/tox.ini
+++ b/tox.ini
@@ -50,6 +50,7 @@ commands = python setup.py testr --slowest --testr-args='--concurrency=1 {posarg
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
 show-source = True
+enable-extensions = H203,H106
 ignore = E123,E125
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build