PDFkit Gem не работает в Rails

Я установил PDFKit и wkhtmltopdf. Я использовал brew install для wkhtmltopdf, а для PDFkit я добавил его в свой файл gem и создал следующее:

# config/initializers/pdfkit.rb
PDFKit.configure do |config|
  config.wkhtmltopdf = '/usr/local/bin/wkhtmltopdf'
  config.default_options = {
    # :page_size => 'Legal',
    # :print_media_type => true
  }
  # config.root_url = "http://localhost" # Use only if your external hostname is unavailable on the server.
end

а также добавил следующее в application.rb

require 'pdfkit'
config.middleware.use PDFKit::Middleware

когда я запускаю which wkhtmltopdf, я получаю: /usr/local/bin/wkhtmltopdf

и я также могу запустить wkhtmltopdf google.com google.pdf, и он правильно загружает файл.

Я даже могу сделать что-то вроде wkhtmltopdf http://localhost:3000/about google.pdf, и это прекрасно работает.

Однако, если я попытаюсь сделать: http://localhost:3000/about.pdf и просто зайду туда в своем браузере, весь веб-сайт просто попытается загрузиться и никогда не завершится. Однако я получаю следующее:

RuntimeError (command failed: "/usr/local/bin/wkhtmltopdf" "--quiet" "-" "-"):
  pdfkit (0.5.2) lib/pdfkit/pdfkit.rb:71:in `to_pdf'
  pdfkit (0.5.2) lib/pdfkit/middleware.rb:21:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
  rack (1.4.1) lib/rack/etag.rb:23:in `call'
  rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/head.rb:14:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/flash.rb:242:in `call'
  rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
  rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/cookies.rb:338:in `call'
  activerecord (3.2.3) lib/active_record/query_cache.rb:64:in `call'
  activerecord (3.2.3) lib/active_record/connection_adapters/abstract/connection_pool.rb:467:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
  activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `_run__1600846312864942852__call__3683691454379641054__callbacks'
  activesupport (3.2.3) lib/active_support/callbacks.rb:405:in `__run_callback'
  activesupport (3.2.3) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
  activesupport (3.2.3) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (3.2.3) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/reloader.rb:65:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
  railties (3.2.3) lib/rails/rack/logger.rb:26:in `call_app'
  railties (3.2.3) lib/rails/rack/logger.rb:16:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/request_id.rb:22:in `call'
  rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
  rack (1.4.1) lib/rack/runtime.rb:17:in `call'
  activesupport (3.2.3) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
  rack (1.4.1) lib/rack/lock.rb:15:in `call'
  actionpack (3.2.3) lib/action_dispatch/middleware/static.rb:62:in `call'
  railties (3.2.3) lib/rails/engine.rb:479:in `call'
  railties (3.2.3) lib/rails/application.rb:220:in `call'
  rack (1.4.1) lib/rack/content_length.rb:14:in `call'
  railties (3.2.3) lib/rails/rack/log_tailer.rb:14:in `call'
  rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service'
  /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
  /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
  /usr/local/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'

и просто чтобы подтвердить, что он находится в промежуточном программном обеспечении.

rake middleware
use ActionDispatch::Static
use Rack::Lock
use #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x007fc11b9c4a30>
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::DebugExceptions
use ActionDispatch::RemoteIp
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use ActionDispatch::ParamsParser
use ActionDispatch::Head
use Rack::ConditionalGet
use Rack::ETag
use ActionDispatch::BestStandardsSupport
use PDFKit::Middleware
run Teacherjoy::Application.routes

Чего мне не хватает, чтобы заставить это работать?