diff --git a/requirements_dev.txt b/requirements_dev.txt
index a27fde4..f18ff79 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==3.7.7
-tox==3.9.0
+tox==3.12.1
 coverage==4.5.3
 Sphinx==2.0.1
 cryptography==2.7