You might want to hold off until after he sheds. Some will feed while in shed, and some won't.

I don't feed when they're in shed. Some of my snakes will take it. However, after having one of my snakes in shed once latch on to the rubber tongs instead of the mouse, I prefer not to feed when they're in shed (didn't realize she was in the milky eyes stage until after she'd grabbed on. It was my colubrid, not one of the balls.)