diff --git a/tox.ini b/tox.ini
index d4326f4..2ace704 100644
--- a/tox.ini
+++ b/tox.ini
@@ -43,15 +43,16 @@ commands =
     coverage report --show-missing
 
 [flake8]
+show-source = True
+# H904: Delay string interpolations at logging calls
+enable-extensions = H106,H203,H904
 # E123, E125 skipped as they are invalid PEP-8.
 # [H106] Don’t put vim configuration in source files
 # [H203] Use assertIs(Not)None to check for None
 # [W504] line break after binary operator
-show-source = True
 ignore = E123,E125,W504
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
-enable-extensions = H106,H203
 
 [hacking]
 import_exceptions =