Had the same problem. This worked 1. uninstalling haskell-cabal with apt
2. installing it agains with curl curl -sSL https://get.haskellstack.org/ | sh as it is recommended (https://docs.haskellstack.org/en/stable/README /#how-to-install) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1786197 Title: stack 1.5.1 broken on 18.04 (AesonException) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/haskell-stack/+bug/1786197/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs