ruby-on-rails - プロダクション モードでパス ヘルパーが見つからない

Question

運用モードの Ruby アプリで 500 内部サーバー エラーが発生します。

Started GET "/invoices/4" for 99.236.159.34 at 2013-07-04 03:48:28 +0000
Processing by InvoicesController#show as HTML
  Parameters: {"id"=>"4"}
  Rendered invoices/show.html.erb within layouts/application (3.3ms)
Completed 500 Internal Server Error in 7ms

ActionView::Template::Error (undefined method `email_invoice_path' for #<#<Class:0x00000002d9a510>:0x00000002f65980>):
    6: <%= link_to " Print Invoice", '#', onclick: "printpage()", :class => 'btn icon-print' %>
    7: <a class="btn btn" href="#"><i class="icon-tag"></i> Print Label</a>
    8: <a class="btn btn" href="#"><i class="icon-barcode"></i> Print Barcodes</a>
    9: <%= link_to " E-mail", email_invoice_path(@invoice), class: "btn icon-envelope" %>
    10:   </div>
    11: <h4>Detail</h4>
    12: <dl class="dl-horizontal">
  app/views/invoices/show.html.erb:9:in `_app_views_invoices_show_html_erb__548775152257063458_24219280'

私のレーキルートは正しいようです:

        email_invoice        /invoices/:id/email(.:format)            invoices#send_email
                      GET    /invoices(.:format)                      invoices#index
                      POST   /invoices(.:format)                      invoices#create
                      GET    /invoices/new(.:format)                  invoices#new
                      GET    /invoices/:id/edit(.:format)             invoices#edit
                      GET    /invoices/:id(.:format)                  invoices#show
                      PUT    /invoices/:id(.:format)                  invoices#update
                      DELETE /invoices/:id(.:format)                  invoices#destroy

ルートコードは次のとおりです。

  resources :invoices do
    member do
      match 'email' => 'invoices#send_email', :as => :email
    end
  end

奇妙なことに、email_invoice_path はローカルでは開発モードでは問題なく動作しますが、本番モードのサーバーでは動作しません。