Array unshift and save to database

Hello,

I’ve noticed that I can’t save my object to the DB after using ‘unshift’
on one of Array fileds. Ex:

(below ‘tags’ is a collection in object ‘transaction’)

transaction.tags.unshift(Tag.find_or_create_by_name(name))
transaction.save!

Everything is fine when I am using ‘<<’ to append tag to array.

Regards