RoR Association Problem

========== Example of problem ==========
@user = User.create(gid: foo, permissions: bar)
@gapiToken = @user.gapiToken.create(access_token: foo, token_type: bar, expires_on: bazz, refresh_token: bop)
#^ Error ^ "undefined method `create' for nil:NilClass"

========== Models ==========
#./app/models/user.rb
class User < ActiveRecord::Base
  has_many :userSessions
  has_one :gapiToken
end


#./app/models/user_session.rb
class UserSession < ActiveRecord::Base
  belongs_to :user
end


#./app/models/gapi_token.rb
class GapiToken < ActiveRecord::Base
  belongs_to :user
end


========== Migrations ==========
#./db/migrate/xxxxxx_create_users.rb
class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string :gid
      t.string :permissions

      t.timestamps
    end
  end
end


#./db/migrate/xxxxxx_create_user_sessions.rb
class CreateUserSessions < ActiveRecord::Migration
  def change
    create_table :user_sessions do |t|
      t.belongs_to :user
      t.string :sid
      t.string :secret
      t.datetime :expires_on

      t.timestamps
    end
  end
end


#./db/migrate/xxxxxx_create_gapi_tokens.rb
class CreateGapiTokens < ActiveRecord::Migration
  def change
    create_table :gapi_tokens do |t|
      t.belongs_to :user
      t.string :access_token
      t.string :token_type
      t.datetime :expires_on
      t.string :refresh_token

      t.timestamps
    end
  end
end