UINavigationBar fades when pushing/popping

Question

I am using the old (pre-iOS7) push/pop animation by using the method described here:

@implementation UINavigationController (Retro)

- (void)pushViewControllerRetro:(UIViewController *)viewController {
    CATransition *transition = [CATransition animation];
    transition.duration = 0.25;
    transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    transition.type = kCATransitionPush;
    transition.subtype = kCATransitionFromRight;
    [self.view.layer addAnimation:transition forKey:nil];

    [self pushViewController:viewController animated:NO];
}

- (void)popViewControllerRetro {
    CATransition *transition = [CATransition animation];
    transition.duration = 0.25;
    transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    transition.type = kCATransitionPush;
    transition.subtype = kCATransitionFromLeft;
    [self.view.layer addAnimation:transition forKey:nil];

    [self popViewControllerAnimated:NO];
}

@end

My problem is that iOS7 seems to fade the UINavigationBar of the previous view controller when pushing a new view controller. Normally this looks fine because iOS 7 is dragging the views on top of each other. But when I am using the pre-iOS7 animation it gives me a short flash, because the navigation bar fades while the new view it getting pushed in from the right side.

Is there a way to disable the fade animation on the navigation bar?