diff --git a/.travis.yml b/.travis.yml
index 111fca0..c47c944 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,7 +22,7 @@ before_install:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install openssl graphviz  ; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install libsasl2-dev python-pip graphviz -y ; fi
   - sudo pip install --upgrade pip
-  - sudo pip install virtualenvwrapper
+  - sudo pip install virtualenvwrapper --ignore-installed six
   - source virtualenvwrapper.sh
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then mkvirtualenv marvin-env         ; fi