rails gem chosen and mailboxes new message

Question

I'm trying to implement chosen gem with mailboxes for new messages. but the select box always appears empty.

messages/new.html.erb

<%= form_tag({controller: "messages", action: "create", 
:class => "form-horizontal"}, method:  :post) do %>     
    <h3>Reply</h3>
    <%= select :recipients,
       User.all.map { |u| [u.name, u.id] },
       { class: 'chosen-select' }
    %>
    <%= text_area_tag :body,nil, class: 'form-control'%>
    <%= submit_tag 'Send message', class: "btn btn-primary" %>
    <% end %>

Messages.js.coffee

$('#messages_recipients').chosen()

js errors:

[Error] ReferenceError: Can't find variable: jQuery (chosen.jquery.js, line 524)
[Error] ReferenceError: Can't find variable: $ (messages.js, line 2)

Can anyone see a problem ? I'm guessing I'm just missing something small, it has been annoying for a rather long time ;/