diff --git a/.travis.yml b/.travis.yml
index fef41c7..195dcaf 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,7 @@ before_install:
 install:
   - pip install --upgrade pip
   - pip install ruamel.yaml
+  - bundle install --path vendor/bundle --quiet
 
 addons:
   apt:
diff --git a/_scripts/travis/cibuild.sh b/_scripts/travis/cibuild.sh
index 1edda8b..1163bde 100644
--- a/_scripts/travis/cibuild.sh
+++ b/_scripts/travis/cibuild.sh
@@ -17,22 +17,20 @@ if [[ $TRAVIS_PULL_REQUEST = "false" ]]; then # triggered by author
 
 else # triggered by Pull Request
 
-  SAFE_DOMAIN=cdn.jsdelivr.net
-
-  bundle install --path vendor/bundle --quiet
+  SAFE_DOMAIN="cdn.jsdelivr.net"
 
   python _scripts/py/init_all.py
 
-  build_cmd="JEKYLL_ENV=production bundle exec jekyll build"
+  build_cmd="bundle exec jekyll build"
 
   echo "\$ $build_cmd"
   eval $build_cmd
 
-  bundle exec htmlproofer --disable-external \
+  bundle exec htmlproofer _site/ \
+            --disable-external \
             --check-html \
             --empty_alt_ignore \
             --allow_hash_href \
-            --url_ignore $SAFE_DOMAIN \
-            _site/
+            --url_ignore $SAFE_DOMAIN
 
 fi