ransack: undefined method `model_name' for Ransack::Search

Hello, I’m running Rails 4.2 and

gem 'ransack', github: 'activerecord-hackery/ransack'

I have the following error:

undefined method `model_name' for Ransack::Search

in here

= simple_form_for @q, method: :get do |form| # This line
  = form.input :region_id_eq, collection: Region.ordered

Here is the action:

  def index
    @q = Wine.search(params[:q])
    @wines = @q.result.page(params[:page])
  end

Backtrace:

NoMethodError - undefined method `model_name' for Ransack::Search<class: Wine, base: Grouping <combinator: and>>:Ransack::Search:
   () Users/zenati/.rvm/gems/ruby-2.1.5@lacavedivry/bundler/gems/ransack-3e4b6e34abc4/lib/ransack/search.rb:113:in `method_missing'
  actionpack (4.2.0) lib/action_controller/model_naming.rb:9:in `model_name_from_record_or_class'
  actionview (4.2.0) lib/action_view/record_identifier.rb:47:in `dom_class'
   () Users/zenati/.rvm/gems/ruby-2.1.5@lacavedivry/bundler/gems/simple_form-749c926140ee/lib/simple_form/action_view_extensions/form_helper.rb:62:in `simple_form_css_class'
   () Users/zenati/.rvm/gems/ruby-2.1.5@lacavedivry/bundler/gems/simple_form-749c926140ee/lib/simple_form/action_view_extensions/form_helper.rb:22:in `simple_form_for'
  app/views/wines/index.html.haml:6:in `_app_views_wines_index_html_haml___3716808230176255752_70261179357660'
  actionview (4.2.0) lib/action_view/template.rb:145:in `block in render'
  activesupport (4.2.0) lib/active_support/notifications.rb:166:in `instrument'
  actionview (4.2.0) lib/action_view/template.rb:333:in `instrument'
  actionview (4.2.0) lib/action_view/template.rb:143:in `render'
  actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:54:in `block (2 levels) in render_template'
  actionview (4.2.0) lib/action_view/renderer/abstract_renderer.rb:39:in `block in instrument'
  activesupport (4.2.0) lib/active_support/notifications.rb:164:in `block in instrument'
  activesupport (4.2.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.2.0) lib/active_support/notifications.rb:164:in `instrument'
  actionview (4.2.0) lib/action_view/renderer/abstract_renderer.rb:39:in `instrument'
  actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:53:in `block in render_template'
  actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
  actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:52:in `render_template'
  actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:14:in `render'
  actionview (4.2.0) lib/action_view/renderer/renderer.rb:42:in `render_template'
  actionview (4.2.0) lib/action_view/renderer/renderer.rb:23:in `render'
  actionview (4.2.0) lib/action_view/rendering.rb:100:in `_render_template'
  actionpack (4.2.0) lib/action_controller/metal/streaming.rb:217:in `_render_template'
  actionview (4.2.0) lib/action_view/rendering.rb:83:in `render_to_body'
  actionpack (4.2.0) lib/action_controller/metal/rendering.rb:32:in `render_to_body'
  actionpack (4.2.0) lib/action_controller/metal/renderers.rb:37:in `render_to_body'
  actionpack (4.2.0) lib/abstract_controller/rendering.rb:25:in `render'
  actionpack (4.2.0) lib/action_controller/metal/rendering.rb:16:in `render'
  actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
  activesupport (4.2.0) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
  /Users/zenati/.rvm/rubies/ruby-2.1.5/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
  activesupport (4.2.0) lib/active_support/core_ext/benchmark.rb:12:in `ms'
  actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
  actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
  activerecord (4.2.0) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
  actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:40:in `render'
  actionpack (4.2.0) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
  actionpack (4.2.0) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
  actionpack (4.2.0) lib/abstract_controller/base.rb:198:in `process_action'
  actionpack (4.2.0) lib/action_controller/metal/rendering.rb:10:in `process_action'
  actionpack (4.2.0) lib/abstract_controller/callbacks.rb:20:in `block in process_action'
  activesupport (4.2.0) lib/active_support/callbacks.rb:117:in `call'
  activesupport (4.2.0) lib/active_support/callbacks.rb:234:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:234:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:234:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `block in halting'
  activesupport (4.2.0) lib/active_support/callbacks.rb:92:in `_run_callbacks'
  activesupport (4.2.0) lib/active_support/callbacks.rb:734:in `_run_process_action_callbacks'
  activesupport (4.2.0) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (4.2.0) lib/abstract_controller/callbacks.rb:19:in `process_action'
  actionpack (4.2.0) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  activesupport (4.2.0) lib/active_support/notifications.rb:164:in `block in instrument'
  activesupport (4.2.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.2.0) lib/active_support/notifications.rb:164:in `instrument'
  actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.2.0) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  activerecord (4.2.0) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.2.0) lib/abstract_controller/base.rb:137:in `process'
  actionview (4.2.0) lib/action_view/rendering.rb:30:in `process'
  actionpack (4.2.0) lib/action_controller/metal.rb:195:in `dispatch'
  actionpack (4.2.0) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.2.0) lib/action_controller/metal.rb:236:in `block in action'
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  warden (1.2.3) lib/warden/manager.rb:35:in `block in call'
  warden (1.2.3) lib/warden/manager.rb:34:in `call'
  rack (1.6.0) lib/rack/etag.rb:24:in `call'
  rack (1.6.0) lib/rack/conditionalget.rb:25:in `call'
  rack (1.6.0) lib/rack/head.rb:13:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/flash.rb:260:in `call'
  rack (1.6.0) lib/rack/session/abstract/id.rb:225:in `context'
  rack (1.6.0) lib/rack/session/abstract/id.rb:220:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/cookies.rb:560:in `call'
  activerecord (4.2.0) lib/active_record/query_cache.rb:36:in `call'
  activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:647:in `call'
  activerecord (4.2.0) lib/active_record/migration.rb:378:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `_run_callbacks'
  activesupport (4.2.0) lib/active_support/callbacks.rb:734:in `_run_call_callbacks'
  activesupport (4.2.0) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (4.2.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/reloader.rb:73:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
  better_errors (2.1.1) lib/better_errors/middleware.rb:84:in `protected_app_call'
  better_errors (2.1.1) lib/better_errors/middleware.rb:79:in `better_errors_call'
  better_errors (2.1.1) lib/better_errors/middleware.rb:57:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  web-console (2.1.0) lib/web_console/middleware.rb:37:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.2.0) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.2.0) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.2.0) lib/active_support/tagged_logging.rb:68:in `block in tagged'
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  railties (4.2.0) lib/rails/rack/logger.rb:20:in `call'
   () Users/zenati/.rvm/gems/ruby-2.1.5@lacavedivry/bundler/gems/quiet_assets-a6fb6e883375/lib/quiet_assets.rb:30:in `call_with_quiet_assets'
  request_store (1.1.0) lib/request_store/middleware.rb:8:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.6.0) lib/rack/methodoverride.rb:22:in `call'
  rack (1.6.0) lib/rack/runtime.rb:18:in `call'
  activesupport (4.2.0) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
  rack (1.6.0) lib/rack/lock.rb:17:in `call'
  actionpack (4.2.0) lib/action_dispatch/middleware/static.rb:113:in `call'
  rack (1.6.0) lib/rack/sendfile.rb:113:in `call'
  railties (4.2.0) lib/rails/engine.rb:518:in `call'
  railties (4.2.0) lib/rails/application.rb:164:in `call'
  rack (1.6.0) lib/rack/content_length.rb:15:in `call'
  unicorn (4.8.3) lib/unicorn/http_server.rb:576:in `process_client'
  unicorn (4.8.3) lib/unicorn/http_server.rb:670:in `worker_loop'
  unicorn (4.8.3) lib/unicorn/http_server.rb:525:in `spawn_missing_workers'
  unicorn (4.8.3) lib/unicorn/http_server.rb:140:in `start'
  unicorn-rails (2.2.0) lib/unicorn_rails.rb:33:in `run'
  rack (1.6.0) lib/rack/server.rb:286:in `start'
  railties (4.2.0) lib/rails/commands/server.rb:80:in `start'
  railties (4.2.0) lib/rails/commands/commands_tasks.rb:80:in `block in server'
  railties (4.2.0) lib/rails/commands/commands_tasks.rb:75:in `server'
  railties (4.2.0) lib/rails/commands/commands_tasks.rb:39:in `run_command!'
  railties (4.2.0) lib/rails/commands.rb:17:in `<top (required)>'
  bin/rails:8:in `<top (required)>'
  spring (1.3.3) lib/spring/client/rails.rb:27:in `call'
  spring (1.3.3) lib/spring/client/command.rb:7:in `call'
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  spring (1.3.3) bin/spring:48:in `<top (required)>'
  spring (1.3.3) lib/spring/binstub.rb:11:in `<top (required)>'
  bin/spring:13:in `<top (required)>'
  bin/rails:3:in `<main>'