captcha in a belongs_to

Hi     I am using simple_captcha. I have two models User and Staff. Relation ship are

User has_one staff staff belongs_to user

     Now in the staff edit I have to include a captcha. I did like

<% form_for @user, :url => staff_url(@staff), :html => {:method => :put } do |f|%>     <p>       <%= f.text_field :first_name,:maxlength => 50 %>     </p>     <p>       <%= show_simple_captcha :image_style => 'random',:distortion => 'medium' %>     </p> <%end %>

   And in staff.rb apply_simple_captcha :message => "Verification code does not match with image."

  And in update action of of staff controller

  def update     @staff = Staff.find(params[:id])     @user = @staff.user       if @staff.valid_with_captcha? and @user.update_attributes(params[:user])         flash[:notice] = "check your mail "         redirect_to login_url       else         flash.now[:error] = @staff.errors.full_messages.join("<br />") #This I wrote deliberately         render :action => :edit       end   end

But even I put the correct captcha code and submit , it always shows message "Verification code does not match with image.". Dont know why please help

Note:

       The params are like {"user"=>{"first_name"=>"Tom", "last_name"=>""}, "action"=>"update", "_method"=>"put", "authenticity_token"=>"0OWRFPssTgTqCUESex7LrJ2QQ7HWSiAQxtiMhQm/N1s=", "captcha"=>"PYESEZ", "id"=>"10", "controller"=>"staff"}

Thanks in advance Tom

Hi   Anybody please help. This still i can't solve

Tom