```ruby
module Faraday
  class Response::Parse < Response::Middleware
    begin
      require 'multi_json'
      require 'multi_xml'
    rescue LoadError, NameError => error
      self.load_error = error
    end

    def self.register_on_complete(env)
      env[:response].on_complete do |response|
        response[:body] = begin
          case response[:response_headers]['content-type']
          when /application\/json/
            parse_json(response[:body])
          when /application\/xml/
            parse_xml(response[:body])
          else
            ''
          end
        end
      end
    end

    def initialize(app)
      super
      @parser = nil
    end

    private

    def self.parse_json(response_body)
      case response_body
      when ''
        nil
      when 'true'
        true
      when 'false'
        false
      else
        ::MultiJson.decode(response_body)
      end
    end

    def self.parse_xml(response_body)
      ::MultiXml.parse(response_body)
    end
  end
end
```

Allow capitalized content-type response header
user
```ruby
module Faraday
  class Response::Parse < Response::Middleware
    begin
      require 'multi_json'
      require 'multi_xml'
    rescue LoadError, NameError => error
      self.load_error = error
    end

    def self.register_on_complete(env)
      env[:response].on_complete do |response|
        response[:body] = begin
          case response[:response_headers].values_at('content-type', 'Content-Type').first
          when /application\/json/
            parse_json(response[:body])
          when /application\/xml/
            parse_xml(response[:body])
          else
            ''
          end
        end
      end
    end

    def initialize(app)
      super
      @parser = nil
    end

    private

    def self.parse_json(response_body)
      case response_body
      when ''
        nil
      when 'true'
        true
      when 'false'
        false
      else
        ::MultiJson.decode(response_body)
      end
    end

    def self.parse_xml(response_body)
      ::MultiXml.parse(response_body)
    end
  end
end
```
assistant