Haddock fails with "Module defined in multiple files"

Hi, We just got a bug report over at Haddock Trac[1]. What's not mentioned is that it works fine for the user on GHC 7.6.3 with Haddock 2.13.1. I can't think of any Haddock changes that could have potentially caused the reported breakage. This e-mail is to ask whether any Cabal(-install) devs can think of anything that might have changed on your end of things that could cause this before we go off chasing a bug in the wrong project. I don't follow the changes in cabal (even though I should) so it might be something really obvious that changed recently that we aren't aware of. Thanks [1]: http://trac.haskell.org/haddock/ticket/284 -- Mateusz K.