creating instance with association doesn't work against AR3.2.1

[kakutani]

Against AR 3.2.1, creating AR instance with association like Employee.create!(... :company => c) doesn't work and raise ActiveModel::MissingAttributeError (same on #new and #create).

I added that as an example on kakutani/enumerated_attribute@d885ac0.
That will success against AR 3.1.3 and fail against AR 3.2.1 (ran against cb915e2).
(I think related commit is rails/rails@50d395f.)

I've just fixed this issue on kakutani/enumerated_attribute@942087b,
but I'm not sure this way is correct or not.

Any idea how I can fix this issue?
Thanks in advance.