import - Adding backwards compatibility for iOS 7 failing due to framework -

import - Adding backwards compatibility for iOS 7 failing due to framework -

i have app utilizes ios 8's new touch id using:

#import "localauthentication/localauthentication.h"

but @ startup on ios 7, app crashes. not phone call touch id programme if not running on ios 8+. log tells me importing framework, have framework set optional, should work unless missed step... why log tell me otherwise?

ios import frameworks ios8