diff --git a/.travis.yml b/.travis.yml
index 5af22b933..e6563f0fe 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@ before_install:
   - git submodule update --remote
 
 install:
+  - pip install six
   - pip install flake8
   - pip install jupyter
   - pip install -r requirements.txt