```ruby
=begin
Copyright 2013 Andrey “A.I.” Sitnik <andrey@sitnik.ru>,
sponsored by Evil Martians.

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
=end

require 'sprockets/railtie'

module AutoprefixedRails
  class Railtie < ::Rails::Railtie
    rake_tasks do |app|
      require 'rake/autoprefixer_tasks'
      Rake::AutoprefixerTasks.new(browsers(app))
    end

    initializer :setup_autoprefixer do |app|
      AutoprefixerRails.install(app.assets, browsers(app))
    end

    # Read browsers requirements from application config
    def browsers(app)
      file   = app.root.join('config/autoprefixer.yml')
      config = file.exist? ? YAML.load_file(file) : { 'browsers' => nil }
      config['browsers']
    end
  end
end
```

Fix Rails initializer without Sprockets
user
```ruby
=begin
Copyright 2013 Andrey “A.I.” Sitnik <andrey@sitnik.ru>,
sponsored by Evil Martians.

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
=end

begin
  require 'sprockets/railtie'

  module AutoprefixedRails
    class Railtie < ::Rails::Railtie
      rake_tasks do |app|
        require 'rake/autoprefixer_tasks'
        Rake::AutoprefixerTasks.new(browsers(app))
      end

      initializer :setup_autoprefixer do |app|
        AutoprefixerRails.install(app.assets, browsers(app))
      end

      # Read browsers requirements from application config
      def browsers(app)
        file   = app.root.join('config/autoprefixer.yml')
        config = file.exist? ? YAML.load_file(file) : { 'browsers' => nil }
        config['browsers']
      end
    end
  end
rescue LoadError
end
```
assistant