diff --git a/tox.ini b/tox.ini
index 9961f3b..6b7c214 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-minversion = 2.0
+minversion = 3.18.0
 envlist = pep8,py3
 ignore_basepython_conflict = true
 
@@ -14,7 +14,7 @@ deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/up
 commands =
     find . -type f -name "*.pyc" -delete
     /bin/bash run_tests.sh -N --no-pep8 {posargs}
-Allowlist_externals =
+allowlist_externals =
   find
   /bin/bash
 
@@ -43,8 +43,10 @@ commands =
   sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:debug]
-Allowlist_externals = oslo_debug_helper
-commands = oslo_debug_helper -t mistraldashboard/test {posargs}
+allowlist_externals =
+  oslo_debug_helper
+commands =
+  oslo_debug_helper -t mistraldashboard/test {posargs}
 
 [flake8]
 show-source = True