Multiple t.references get nil with nested models

I am using devise for users

user belongs_to shop user has_many tasks

shop has_many users shop has_many tasks

task belongs_to user task belongs_to shop

when I create a new task:

current_user.tasks.create(...)

the shop_id gets the value of nil, when I need to be the same shop_id as the user.

when I create a new task

  current_user.shop.tasks.create(...)

I get the user_id as nil but gets the right value for the shop_id.

what am I am missing?

thanks in advance.