Ah, sorry this diff isn't very clear. This is in the documentation for the ``fields_for`` method. Here's what it looked like before:

```ruby
      #   <%= form_for @person do |person_form| %>
      #     First name: <%= person_form.text_field :first_name %>
      #     Last name : <%= person_form.text_field :last_name %>
      #
      #     <%= fields_for :permission, @person.permission do |permission_fields| %>
      #       Admin?  : <%= permission_fields.check_box :admin %>
      #     <% end %>
      #
      #     <%= f.submit %>
      #   <% end %>
```

I'm just changing the ``<%= f.submit %>`` to correct an error.