Kitty Missed the Litterbox this morning

My youngest boy Charlie likes to back himself up against the litterbox. (I'm sure others do this). Well this morning, he missed the corner completely and went poopie on the little ledge where they crawl in and out of the covered box. This is the first time this has ever happened. He was at the vet a few months ago and was fine. Should I be concerned about this? Or was it just a fluke that he backed himself up too far?

Thanks.

Im sure it was just an error

Yeah i reckon poor Charlie did'nt aim correctly, bless him!

That happens once in a while at my house also. I wouldn't be concerned unless this starts consistenly!