Cot bed sheet on Cot size mattress?

[Hellokitty]

I found a fitted sheet to co-ordinate with Maia's cot bumper but it only comes in cot-bed size and Maia is in a cot.

Just wondered if anyone had tried to put a cot-bed size sheet on a cot size mattress and whether it looks ok, or all saggy?

Cheers. x