diff --git a/requirements_dev.txt b/requirements_dev.txt
index 45557f4..2d1b293 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -2,7 +2,7 @@ pip==20.1.1
 bump2version==1.0.0
 wheel==0.34.2
 watchdog==0.10.2
-tox==3.15.1
+tox==4.21.2
 flake8==3.8.2
 coverage==5.1
 Sphinx==3.0.4