Ruby on Rails

I have  a nested model  Place => Geolocation

class Place < ActiveRecord::Base

  has_one :geolocation, :dependent => :destroy

  accepts_nested_attributes_for :geolocation, :reject_if => :all_blank, :allow_destroy => true

  attr_accessible :geolocation_attributes

class Geolocation < ActiveRecord::Base

  belongs_to :place

----------------------

Creating Place + Geolocation  is ok ,  

= simple_form_for  @place, :url => backoffice_places_path, :html => {:class => 'form-vertical' } do |f|

   ...

   = f.simple_fields_for :geolocation do |g|

         = render "geolocation_fields", :f => g

Editing Place + geolocation doesnt pass ,   the update method  receives the new geolocation attributes from the form, but the geolocation instance is not updated... ( no validation error )

=  simple_form_for @place, :url => backoffice_place_path, :html => {:method => :put, :class => 'form-vertical' } do |f|

   ...

    = f.simple_fields_for :geolocation_attributes, @place.geolocation  do |g|

 = render "geolocation_fields", :f => g

Place controller 

  def edit

     @place = Place .find(params[:id])

    

  def update

    debugger

    if @place.update_attributes(params[:place])

      debugger

      redirect_to backoffice_place_path(@place), notice: t(:place_updated)

params

{"id"=>"76", "geolocation_attributes"=>{"street_address"=>"19 Camp Road", "postal_code"=>"Greater London SW19 4UW", "city"=>"London", "country"=>"United Kingdom"}, "controller"=>"backoffice/places", "action"=>"update"}

any ide where I am wrong  ?  thanks for any clue