diff --git a/.travis.yml b/.travis.yml
index 63f0b5a..e10837f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -39,7 +39,7 @@ matrix:
 sudo: false
 
 install:
-- travis_retry pip install tox==2.1.1
+- travis_retry pip install tox
 - travis_retry pip install coverage
 
 script: tox