Updates
Summary I tried rebuilding today after 7 months of forgetting how this works and when I tried to jekyll build I got $ jekyll build Traceback (most recent call last): ... /usr/local/Cellar/ruby/2.6.5/lib/ruby/2.6.0/bundler/lockfile_parser.rb:108:in `warn_for_outdated_bundler_version': You must use Bundler 2 or greater with this lockfile. (Bundler::LockfileError) Per this answer, I ran gem list bundler to see my rubygems version and then gem update --system $ gem list bundler *** LOCAL GEMS *** bundler (2.0.2, 1.17.2) $ gem update --system Updating rubygems-update Fetching rubygems-update-3.1.3.gem Successfully installed rubygems-update-3.1.3 ... ... RubyGems installed the following executables: /usr/local/Cellar/ruby/2.6.5/bin/gem /usr/local/Cellar/ruby/2.6.5/bin/bundle RubyGems system software updated Now I get $ gem list bundler *** LOCAL GEMS *** bundler (default: 2.1.4, 2.0.2, 1.17.2) $ And now my jekyll build worked!