I asked around a bit, and I learned that that may be acceptable in some contexts for some natives (Scottish especially), but not here. Well, deleted from here, but we added it in many places, hard to delete it everywhere one by one. We probably won't accept it in Tree 2.0. Will see.
Take a look here: https://www.duolingo.com/comment/19529552$comment_id=19554885 :)