diff --git a/tox.ini b/tox.ini
index de5d4a4..90bfb91 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-minversion = 3.1
+minversion = 3.18.0
 envlist = py3,pep8
 
 [testenv]