GitHub Pages Jekyll hosted blog doesn't pick up remote_theme

Question

I've just installed a Jekyll blog and I've tested it locally with a remote_theme and locally, it works fine. However when it's being deployed to GH page I see that the theme is minima (the default one).

In my _config.yml:

remote_theme: benbalter/retlab
plugins:
  - jekyll-remote-theme
  - jekyll-feed
  - jekyll-include-cache

In my Gemfile:

group :jekyll_plugins do
  gem "github-pages"
  gem "jekyll-feed"
  gem "jekyll-include-cache"
  gem 'jekyll-sitemap'
  gem 'jekyll-seo-tag'
end

gem "jekyll-remote-theme"

I have also tried to change the url and baseUrl in _config.yml and the result is exactly the same. I also tried to use other themes such as remote_theme: "mmistakes/[email protected]" and the result is exactly the same.

Thanks!