"Can't mass-assign protected attributes" with nested attributes

I've seen other questions with this problem, but so far the answers haven't worked for me. I'm trying to have a form that registers a User, and creates an Organization at the same time. The User and Organization are associated via an assignment table. Here is my form: ``` = form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| = devise_error_messages! = f.fields_for :organizations do |f| = f.label :name = f.text_field :name = f.label :email = f.email_field :email = f.label :password = f.password_field :password = f.label :password_confirmation = f.password_field :password_confirmation ``` My Registration controller: ``` class Users::RegistrationsController < Devise::RegistrationsController def new @user = User.new @user.organizations.build end def create super end def update super end end ``` My Organization model: ``` class Organization < ActiveRecord::Base has_many :organization_assignments has_many :users, :through => :organization_assignments attr_accessible :name end ``` and my User model: ``` class User < ActiveRecord::Base has_many :organization_assignments has_many :organizations, :through => :organization_assignments # Include default devise modules. Others available are: # :token_authenticatable, :confirmable, # :lockable, :timeoutable and :omniauthable devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable accepts_nested_attributes_for :organizations # Setup accessible (or protected) attributes for your model attr_accessible :email, :password, :password_confirmation, :remember_me, :organization_attributes # attr_accessible :title, :body end ``` The exact error I'm getting is: Can't mass-assign protected attributes: organizations_attributes