diff --git a/.travis.yml b/.travis.yml
index c7dbffba71..c7a7571c1d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,6 +15,7 @@ jobs:
       install:
         - gem install asciidoctor
         - gem install asciidoctor-diagram
+        - gem install rouge
       script:
         - chmod +x ./scripts/check-asciidoctor-build.sh
         - ./scripts/check-asciidoctor-build.sh