diff --git a/requirements_dev.txt b/requirements_dev.txt
index a3b05871..1c666dc4 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -3,7 +3,7 @@ bumpversion==0.6.0
 wheel==0.34.2
 watchdog==0.9.0
 flake8==3.8.3
-tox==3.15.0
+tox==3.20.0
 coverage==5.0.4
 Sphinx==3.2.1
 cryptography==2.8