diff --git a/requirements.txt b/requirements.txt
index 6ca5fa01c..b62ff07df 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -8,6 +8,6 @@ flake8==3.6.0
 
 # Testing
 # ------------------------------------------------------------------------------
-tox==3.5.2
+tox==3.5.3
 pytest==3.9.3
 pytest-cookies==0.3.0