diff --git a/requirements.txt b/requirements.txt
index d16abf2..3f5e6dc 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,7 +2,7 @@ pip==18.0
 bumpversion==0.5.3
 wheel==0.31.1
 watchdog==0.8.3
-tox==3.1.3
+tox==4.18.0
 flake8==3.5.0
 Sphinx==1.7.6
 PyYAML==3.13