DEPRECATION WARNING: @picture will no longer be implicitly assigned to picture. 
(called from tag at /usr/path/actionpack-2.3.5/lib/action_view/helpers/active_record_helper.rb:250)

Fix is easy – just use @picture not picture. In future Rails versions you will always need to add “@”.

Template part with code raising this warning:

<div class="form_row picture">
<% fields_for "pictures[]", @picture do |picture_form| %>
  <label><%= t('attribute.description') %>:</label>
  <%= picture_form.text_field :description %>
  <%= picture_form.file_field :picture %>
<% end %>
</div>