Why we can't use iPhoto pictures on screen saver anymore?

After years of using our personal pictures from iPhoto for our screen saver, our Mac won't let us choose iPhoto Library as our source for the screen saver anymore. Does anyone know why this happened? When I choose a folder, the iPhoto Library is dim and won't allow it as a selection. Photo Booth is an option, but not iPhoto Library. This has been our screen saver for years. I didn't change it and don't know why the change occurred. And now I can't figure out how to change it back.