diff --git a/requirements_dev.txt b/requirements_dev.txt
index 511ae97..cd4677c 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -2,7 +2,7 @@ pip==18.0
 wheel==0.32.1
 watchdog==0.9.0
 flake8==3.5.0
-tox==3.5.2
+tox==3.5.3
 coverage==4.5.1
 Sphinx==1.8.1
 twine==1.12.1