The error message from a missing ! is re-appearing with ghc-7.4.2. I've attached a patch to fix this. I think it's compatible through at least ghc-6.12.3 (the earliest version I have available), as well as without ghc extensions.
issue #2 - fix warning message due to missing !
Thanks - I've fixed it in a different way (I want to avoid needing to enable BangPatterns).