How do I stop AppleTV showing media title on iPhone?

When I play media on my AppleTV it shows up on the lock screen in my iPhone. Even though what I'm watching on my TV should be totally private to me, if I use my phone at work or in mixed company that info, that should have stayed at home, shows up for others to see. This is not very privacy oriented. How can I turn off this info sharing and keep my TV viewing only on my TV?