Both my kids have done this from time to time, If they slept past 5 I would wake them up otherwise they would wake up on their own and not get back to sleep til late. I've generally kept them awake til around 11.30am and then put them down for a nap after having something to eat. I found that If I put them down any later they would sleep too long then be awake all night... not fun.

(from around 11 months they both only had 1 nap a day)