diff --git a/requirements_dev.txt b/requirements_dev.txt
index a3dc814..d3a9128 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -3,7 +3,7 @@ bump2version==0.5.11
 wheel==0.33.6
 watchdog==0.9.0
 flake8==3.7.8
-tox==3.14.0
+tox==4.23.1
 coverage==4.5.4
 Sphinx==1.8.5
 twine==1.14.0