Assignment hard "cutoff" date not working

[fstonedahl]

I have tried creating assignments using the checkbox:

This is a cutoff date
If selected, the student will lose write access to their repository after the date is reached.

However, it is not working as documented. Students do not lose write access, and they can continue to push their work after the due date. (It does get marked as "late" in the classroom dashboard, but student write access is not removed.)