Hi Simon, Sorry for the broken build again. Since your last email I do run a nightly build, but you were about an hour and a half before today’s build! Anyway, I believe the offending commit is 8c6a3d68c0301bb985aa2a462936bbcf7584ae9c , This unconditionally adds GHC.Event which then includes that TimerManager which is defined for POSIX only. Reverting that should get you building again. Cheers, Tamar From: Simon Peyton Jones via ghc-devs Sent: Friday, October 14, 2016 22:38 To: ghc-devs@haskell.org Subject: Aargh! Windows build is broken AGAIN I really wish I did not have to be the Windows integration server. Currently, from a clean build of HEAD, I’m getting libraries\base\GHC\Event\TimerManager.hs:62:3: error: error: #error not implemented for this operating system # error not implemented for this operating system ^ I’d revert something if I could, but I can’t see what to revert. Help, please! Simon