Thanks for the fast and detailed response! Makes total sense that KVO is meant to access properties only, but until now it was/is not forced for other methods than -copy. If I extend my class and define a method like: - (Sample *)notCrashing { return [self copy]; } and call it like [@[[Sample new]] valueForKey:@"notCrashing"]; it also returns a +1 ref count object, but it does not crash on iOS 17. Or do I misunderstand? Anyway I will change all places where KVC is used in that way before iOS 17 will be released to avoid crashes :-)

Yes, you are right. I checked again and ARC is adding an autorelease to -notCrashing. Thanks for the clarification.