diff --git a/.travis.yml b/.travis.yml
index 88bef0e..9de22be 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,6 +3,7 @@ php:
   - '5.4'
   - '5.6'
   - '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