When pulling back info on a closed question, I have come to expect closed_reason to be a present key if there's a closed_date. It seems that as of recently this is no longer true.

Proof: https://api.stackexchange.com/2.1/questions/164867?pagesize=10&site=askubuntu

What happened to this key? I need it. Can it be reintroduced please?

Edit: Just noticed this is still in the API documentation, so I guess this is more of a bug. Again, please add this back to the API. We need it as part of Ask Ubuntu's ongoing cleanup effort.