update_attribute does not call attribute=

With ActiveRecord, you can override attribute= and it will be called for anything other than write_attribute to set the field. I need this behavior, but it is not happening in Mongoid 3.1.4.

I have:

field :is_primary, type: Boolean, default: false
def is_primary=(bool)
disable_others if bool
super(bool)
end

When I call update_attribute(:is_primary, true) the value is updated in the database, but my function is never called so disable_others is never called.

It appears this is caused by update_attribute calling write_attribute(name, value) instead of {{send("#

=", value)}}. See ActiveRecord::Persistence#update_attribute