Can't mass-assign protected attributes: profiles,

I read lot of related posts but can't find why it's not working for me. I still have a "can't mass-assign protected attributes: profiles"... What am I doing wrong ? I have a User model and a related Profile model with a one-to-one relationship. Here the User model (simplified) ``` class User < ActiveRecord::Base attr_accessible :email, :password, :password_confirmation, :profile_attributes, :profile_id has_secure_password has_one :profile accepts_nested_attributes_for :profile end ``` the Profile model ``` class Profile < ActiveRecord::Base attr_accessible :bio, :dob, :firstname, :gender, :lastname, :user_id belongs_to :user end ``` my User controller ``` def new @user = User.new respond_to do |format| format.html # new.html.erb format.json { render json: @user } end end def create @user = User.new(params[:user]) @user.build_profile respond_to do |format| if @user.save format.html { redirect_to @user, flash: {success: 'User was successfully created. Welcome !'} } format.json { render json: @user, status: :created, location: @user } else format.html { render action: "new" } format.json { render json: @user.errors, status: :unprocessable_entity } end end end ``` If it can be of any help, both User and Profile were scaffolded. I tried too with ':profiles_attributes' instead of 'profile_attributes' in the User attr_accessible, same problem... tried too, '@user.profiles.build' instead of '@user.build_profile' in the User controller... same result... Any help with some explanation would be great (I'm a noob on rails so forgive me) EDIT The simple form I use ``` <%= simple_form_for(@user) do |f| %> <%= f.error_notification %> <%= f.simple_fields_for :profiles do |p| %> <div class="nested-form-inputs"> <%= p.input :lastname %> <%= p.input :firstname %> </div> <% end %> <div class="form-inputs"> <%= f.input :email %> <%= f.input :password %> <%= f.input :password_confirmation %> </div> <div class="form-actions"> <%= f.button :submit %> </div> <% end %> ``` Cheers