diff --git a/.travis.yml b/.travis.yml
index 5a1ae56..37dc9c1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,12 +2,21 @@ language: ruby
 rvm:
   - 2.4.1
 
+before_install:
+ - export NOKOGIRI_USE_SYSTEM_LIBRARIES=true
+
+addons:
+  apt:
+    packages:
+    - libcurl4-openssl-dev # required to avoid SSL errors
+
 install:
  - cd site/
  - bundle install
 
 script:
  - bundle exec jekyll build --destination ../out/
+ - gem install html-proof && htmlproof ../out/
 
 # branch blocklist, only for GitHub Pages
 branches: