diff --git a/requirements_dev.txt b/requirements_dev.txt
index b1b09cc..3fbe38c 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -2,7 +2,7 @@ bumpversion==0.5.3
 wheel==0.30.0
 watchdog==0.8.3
 flake8==3.5.0
-tox==2.9.1
+tox==4.22.0
 coverage==4.4.1
 Sphinx==1.6.5