diff --git a/requirements_dev.txt b/requirements_dev.txt
index 27cb153..449cbe5 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -3,7 +3,7 @@ bumpversion==0.5.3
 wheel==0.30.0
 watchdog==0.8.3
 flake8==3.4.1
-tox==2.9.1
+tox==4.23.2
 coverage==4.4.1
 Sphinx==1.6.4
 cryptography==2.1.1