Out of sync after app (data model) update

[jphribovsek]

2 iOS devices A and B
App v1.0 is installed on both iOS devices.
Core Data Model has one entity Book with couple of attributes Title and Author

v1.1 is now released and Book now has a new attribute Editor in addition to previous ones.

v1.1 is installed on device A, device B remains on v1.0

One Book is created on device A (v1.1), with a Title, Author and Editor
App is opened on device B (v1.0), object is synced in, editor attribute is skipped since not in data model.

App on device B is then upgraded to v1.1
device A now shows the book with an editor, device B doesn't show the editor, devices are out of sync