Unable to change camera FlashMode for UIImagePickerController

I have a button on my custom camera overlay that calls this method:

- (void) changeFlash:(id)sender
{
    //UIImagePickerControllerCameraFlashModeOff  = -1,
    //UIImagePickerControllerCameraFlashModeAuto = 0,
    //UIImagePickerControllerCameraFlashModeOn   = 1
    NSLog(@"before %d", self.picker.cameraFlashMode);
    switch (self.picker.cameraFlashMode) {
        case UIImagePickerControllerCameraFlashModeAuto:
            [(UIButton *)sender setImage:[UIImage imageNamed:@"flashOn"] forState:UIControlStateNormal];
            self.picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOn;
            break;
        case UIImagePickerControllerCameraFlashModeOn:
            [(UIButton *)sender setImage:[UIImage imageNamed:@"flashOff"] forState:UIControlStateNormal];
            self.picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeOff;
            break;

        case UIImagePickerControllerCameraFlashModeOff:
            [(UIButton *)sender setImage:[UIImage imageNamed:@"flashAuto"] forState:UIControlStateNormal];
            self.picker.cameraFlashMode = UIImagePickerControllerCameraFlashModeAuto;
            break;
    }
    NSLog(@"after %d", self.picker.cameraFlashMode);

}

self.picker.cameraFlashMode is always 0, before and after changing it. What am I doing wrong?

Also, the flash never works, although it is supposedly stuck in UIImagePickerControllerCameraFlashModeAuto.