Jayce does in fact stumble for a moment thanks to the whack and gasp in dramatic horror at it, only to laugh since he was messing around. He is considering that an unspoken 'yes I find you good-looking' answer and therefore going to feel smug about it.

"Fine, fine." Jayce gives in, because making him sleep in is very difficult, but maybe if he blots out everyone option of the sun getting in, it'll make it harder for Viktor to get jolted out of sleep. That's the plan as they head back, exhausted.