diff --git a/requirements_dev.txt b/requirements_dev.txt
index 1c1e1aa..73ad22b 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -3,7 +3,7 @@ bumpversion==0.5.3
 wheel==0.33.4
 watchdog==0.9.0
 flake8==3.7.8
-tox==3.13.2
+tox==3.23.1
 coverage==4.5.4
 Sphinx==2.1.2