diff --git a/requirements_dev.txt b/requirements_dev.txt
index 765264c..34e4e4f 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -13,6 +13,6 @@ sphinx-rtd-theme>=0.5.0
 
 # testing
 flake8>=2.6.0
-tox==4.3.1
+tox==4.3.3
 coverage>=4.3.0
 wget>=3.2