Ubuntu 11.10 comes with this library libgmp.so.10 and previous versions come with libgmp.so.3. When you make ghc --make app.hs, it dynamically links libgmp.so.10. This won't run on 11.04 or earlier with the error message libgmp.so.10 not found. So, I compiled using ghc -static -optl-static -optl-pthread --make app.hs. ( http://stackoverflow.com/questions/7344744/haskell-program-built-on-ubuntu-1... got it running). I even ran ldd to check dependencies: ldd app not a dynamic executable Now, it fails with app: mkTextEncoding: invalid argument (Invalid argument) I'm trying to deploy to Heroku. Here's the repository: https://github.com/abdulsattar/hkonhk. Here's the heroku app: http://hkonhk.herokuapp.com/ And here's the output of heroku log (after the push): 2011-12-30T07:13:58+00:00 heroku[slugc]: Slug compilation started 2011-12-30T07:14:06+00:00 heroku[web.1]: State changed from crashed to created 2011-12-30T07:14:06+00:00 heroku[web.1]: State changed from created to starting 2011-12-30T07:14:06+00:00 heroku[slugc]: Slug compilation finished 2011-12-30T07:14:08+00:00 heroku[web.1]: Starting process with command `./app` 2011-12-30T07:14:08+00:00 app[web.1]: app: mkTextEncoding: invalid argument (Invalid argument) 2011-12-30T07:14:10+00:00 heroku[web.1]: State changed from starting to crashed 2011-12-30T07:14:10+00:00 heroku[web.1]: Process exited 2011-12-30T07:14:11+00:00 heroku[router]: Error H10 (App crashed) -> GET hkonhk.herokuapp.com/ dyno= queue= wait= service= status=503 bytes= I've asked about this many times on #haskell, but I couldn't get it working. Help would be highly appreciated. -- Warm Regards, AbdulSattar Mohammed