diff --git a/.travis.yml b/.travis.yml
index e719591..bc2f678 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,6 @@
 before_install:
  - gem install bundler
  - gem install concurrent-ruby
+ - gem install asciidoctor-pdf --pre
 script:
  - cd docs; make
\ No newline at end of file