But it wasn't until she picked her son up from nursery that day, her teacher pointed out the glaringly obvious.
The brightly-coloured 'Merry Christmas' across the front of the jumper is in fact written in Father Christmas' urine. Nice.
Accidentally sent my son to school wearing his newly bought sweater. Didn't realize what Santa was doing until his kindergarten teacher pointed it out to me when I picked him up.
Her honest mistake has at least lightened up some other people's days on the internet.
"Wow, you know he's the coolest kid in class right now?" commented one person on the photo.
"This is brilliant, where can I get one?" wrote another.
One person rightly asked why they sold this jumper in kids' sizes. Probably for awkward situations like this. Oops.