How to adjust cat's schedule?

About a month ago I started working the night shift. I come home at 6am every day, and I usually want to go straight to bed. Before, my kitten (7 months) would always lie on top of me and we'd sleep together, but he's having a hard time adjusting to my new schedule. As soon as I lay down, he wants to play and the only way I can get him to leave me alone is to lock him out of my room. Obviously I don't want to keep doing that. Any advice on how to teach him that bedtime isn't playtime?