diff --git a/.travis.yml b/.travis.yml
index cd3cbf9..344b68a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,7 +15,7 @@ matrix:
       jdk: openjdk8
     - rvm: jruby-9.2.11.0 # ruby 2.5
       jdk: oraclejdk9
-    - truffleruby-head
+    - rvm: truffleruby-head
     - rvm: 2.3
       install: true # This skips 'bundle install'
       script: gem build rainbow && gem install *.gem