diff --git a/.travis.yml b/.travis.yml
index a97431f..ad8af62 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,3 +5,5 @@ php:
   - '7.0'
   - hhvm # on Trusty only
   - nightly
+before_script:
+  - curl -sSfL -o ~/.phpenv/versions/hhvm/bin/phpunit https://phar.phpunit.de/phpunit-5.7.phar