diff --git a/requirements_dev.pip b/requirements_dev.pip
index 21caa52..7a1717e 100644
--- a/requirements_dev.pip
+++ b/requirements_dev.pip
@@ -3,7 +3,7 @@ bumpversion==0.5.3
 wheel==0.29.0
 watchdog==0.8.3
 flake8==3.3.0
-tox==2.7.0
+tox==3.21.3
 coverage==4.3.4
 cryptography==1.8.1
 PyYAML==3.12