diff --git a/requirements.txt b/requirements.txt
index 66ea9fe..b7f86c9 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ bumpversion==0.5.3
 wheel==0.30.0
 watchdog==0.8.3
 flake8==3.5.0
-tox==2.8.2
+tox==4.23.2
 coverage==4.4.1
 Sphinx==1.7.9
 sphinx-rtd-theme==0.1.9