Rails autopopulates form with database values thus ignoring my model methods

My view:

<%= form_for @product %>
  <%= form.text_area :hi %>
<% end %>

My model:

def hi
  'hello'
end

Which works properly from console - no matter what :hi attribute really is in the database, it's retrieved as 'hello'.

I guess Rails ignores model method overrides when autopopulating forms? How do I make it pay attention to my override?