diff --git a/tox.ini b/tox.ini
index 66897b9aa..60e78c508 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 isolated_build = True
-minversion = 3.3
+minversion = 3.5.3
 distshare = {homedir}/.tox/distshare
 # make sure to update environment list in travis.yml and appveyor.yml
 envlist =