[hawkice]

I think number 12 is passing in a string instead of a [ListItem Char].

[bramgg]

99 Haskell is open source and I haven't tested all of the newer problems myself. I'm out right now on mobile, but if you think you've found an error please don't hesitate to patch it! I've tried to make modifying the problems as easy as possible:

https://github.com/bramgg/99haskell