Hello all, After fiddling around this weekend I've written a quick, comprehensive guide to a Better Build Environment for windows users. It pretty much "Just works" and I think should make it easy to get started with new machines: https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Windows/MSYS2 Many thanks to Kyra for pointing this out to us on the GHC developer list. It is a much nicer to use mingw/msys environment with a lot of bugs fixed, and it's easy to install. Following the instructions should mostly be copy-paste. In particular, this resolves some weird issues with `validate` and traditional `make`, including a horrible deadlocking bug with make (and also 'tee', it seems.) So windows users can build in parallel again and everything works as expected. It also gives a simple and complete guide to build for x86_64 users (we didn't really mention it previously.) Please shout if you have problems. I've tested this with both an x86 and x86_64 build. -- Regards, Austin Seipp, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/