Thanks, yes I know I should add it to the lesson, just too much to do with the course so some things don't get done.
EDIT: It's been added, link here: https://www.duolingo.com/skill/sv/Verbs:-Present-3
Jumper and pullover are also accepted answers. Unfortunately at least in the US, they (at least some people) use shirt to mean pretty much any kind of clothing worn on the upper body, (except like jackets and ties) so we have to accept that too. But I definitely agree with you that jumper is a better translation than shirt.
Could you get away with 'you have a jumper on' or even 'you have a jumoer on you' which you would rarely say in English, but I can think of a time when you would. It just helps me to translate it literally rather than saying 'you are wearing a jumper' All of these would work in English and Austrailian. Not sure about American?