WP Spotify & Facebook Activity Feed

[Monthigos]

I just noticed that nothing is showing up in my Facebook activity feed when I'm listening to Spotify on my Windows Phone.  All I can see is my plays from my laptop.  Under Settings > Social there are two options: Private Session and Scrobble to Last.fm and nothing about Facebook.  I've tried turning Private Session on and off but there is no change.  Is this feature not supported on Windows Phone, or am I just missing a setting somewhere?  Thanks for any information.