Why won't the Quick vibration alert stick in Mail notification settings?

[clankfu]

"Quick" vibration alert won't stick in Mail notification settings

When I try to set my vibration alert for Mail in the notification settings to "Quick", it doesn't stick. I can select it but if I back out and then go back in, the vibration alert is set to "None".

All the other vibration settings work fine. Is this a bug?