--- a/tox.ini	Tue Oct 02 16:04:52 2018 +0200
+++ b/tox.ini	Mon Oct 29 10:09:19 2018 +0100
@@ -18,9 +18,10 @@
   web: {envpython} -m pytest {posargs} {toxinidir}/cubicweb/web/test
 
 [testenv:flake8]
+basepython=python2
 skip_install = true
 deps =
-  flake8 >= 3.5
+  flake8 >= 3.5, < 3.6
 whitelist_externals =
   /bin/sh
 commands = /bin/sh -c "flake8 `xargs -a {toxinidir}/flake8-ok-files.txt`"