diff --git a/.travis.yml b/.travis.yml
index 5797516..ccf20c8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,7 +14,7 @@ matrix:
       env: TOXENV=py36
 
 install:
-  - pip install tox
+  - pip install tox==2.9.1
 
 script:
   - tox