diff --git a/tox.ini b/tox.ini
index 030f05b..c5892f9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 envlist = py3,pypy,pep8
-minversion = 1.6
+minversion = 3.18.0
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
@@ -8,7 +8,6 @@ setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = stestr run --slowest {posargs}
-passenv = *_proxy *_PROXY
 
 [testenv:pep8]
 commands =