How to configure "Revive This Topic"?

This is embarrassing, but I can’t for the life of me figure out where or how I activate and configure the “Revive This Topic?” pop-up that shows when users try to reply to old threads. There’s been a motherlode of necromancing lately on the forum I help administer and people are starting to complain -_- So where in the admin interface do I find this option? I’ve tried searching to no avail.

Update: finally found it. I was searching for the word “revive” when the option was actually called “warn reviving old topic age”. It was only by searching for “old topic” that the option finally appeared.