I'd like to have the page-curl animation when my app runs on iOS 5, for iOS 4-devices I made a custom animation.

I'm setting the spineLocation manually, as it didn't work otherwise (see: [UIPageViewController: pageViewController:spineLocationForInterfaceOrientation: not called](https://stackoverflow.com/questions/7755755/uipageviewcontroller-pageviewcontrollerspinelocationforinterfaceorientation-no)):

```
if ([UIPageViewController class]) {
   NSDictionary *options = [[NSDictionary alloc] initWithObjectsAndKeys:[NSNumber numberWithInt:UIPageViewControllerSpineLocationMid], UIPageViewControllerOptionSpineLocationKey, nil];
   ...

```

But that gives me at runtime on iOS4:

```
 Symbol not found: _UIPageViewControllerOptionSpineLocationKey

```

The code isn't reached on iOS4-devices, nevertheless it crashes with that error message. What can I do to make that work?

Thanks!