UIAlertView in superclass and subclass

I have a superclass where I sometimes show an UIAlertView and handles the delegation (clickedButtonAtIndex). When I then have a subclass that also handles the "clickedButtonAtIndex" only the subclass delegation is called.

In both cases the UIAlertView is show like this:

[[[UIAlertView alloc] initWithTitle:@"" message:@"message" delegate:self cancelButtonTitle:@"Close" otherButtonTitles:@"Open", nil]show];

Am I doing something wrong or is it bad design to have the same delegation in both the superclass and subclass. I thought the "delegate:self" separated them.