iOS 7 MapKit MKAnnotationView's image property type encoding weirdness

iOS 7 MapKit MKAnnotationView's image property type encoding weirdness

These are the results of
method_getTypeEncoding(class_getInstanceMethod(MKAnnotationView.class,
@selector(setImage:)))
method_getTypeEncoding(class_getInstanceMethod(MKAnnotationView.class,
@selector(image)))
7.0:
v12@0:4^{UIImage=#^vf{?=b1b3b1b1b1b16b2}}8
^{UIImage=#^vf{?=b1b3b1b1b1b16b2}}8@0:4
and 6.1:
v12@0:4@8
@8@0:4
I don't understand why it's a ^{... instead of @. It's causing me problems
in Rubymotion.
Thanks in advance!