jekyll-lunr-js-search or one of its dependencies installed

[vjandrei]

I have on GEMFILE
source 'https://rubygems.org'
group :jekyll_plugins do
gem 'jekyll-sitemap'
gem 'autoprefixer-rails'
gem 'jekyll-assets'
gem 'jekyll-github-metadata'
gem 'github-pages'
gem 'jekyll-lunr-js-search'
end

group :development do
gem 'capistrano', '> 3.4.0'
gem 'capistrano-rails', '> 1.1.3'
gem 'capistrano-rbenv', '~> 2.0.3'
gem 'capistrano-passenger'
end

On _config
gems: ['jekyll-lunr-js-search', 'jekyll-sitemap', 'jekyll-github-metadata']

And when I try to run jekyll serve
jekyll serve
Configuration file: _config.yml
Dependency Error: Yikes! It looks like you don't have jekyll-lunr-js-search or one of its dependencies installed. In order to use Jekyll as currently configured, you'll need to install this gem. The full error message from Ruby is: 'cannot load such file -- jekyll-lunr-js-search' If you run into trouble, you can find helpful resources at http://jekyllrb.com/help/!
jekyll 3.1.2 | Error: jekyll-lunr-js-search

[tedsanders]

Trying to use the plugin and ran into the same problem on step 1b. No clue why there's a dependency error. Suggestions appreciated.