Hello, does something change on Rails 2.0.2 about the using of error_messages_for helper ???

I have just started a new project on 2.0.2 (the first one with this Rails version) and I did, like always

app_controller
Code:
  def add_category
      @category = Category.new(params[:category])

      if request.post? and @category.save
        flash[:notice] = 'Category successfully created'
      end
      
       redirect_to :action => "settings" 
  end
  
end
settings.html.erb
Code:
<%= error_messages_for "category" %>
But it doesn't show any error message.

Thank you