Howdy, I am unable to build the latest revision of GHC on NixOS. I can build older revisions. Here's my error: ===--- building final phase make --no-print-directory -f ghc.mk phase=final all "inplace/bin/ghc-stage1" -hisuf p_hi -osuf p_o -hcsuf p_hc -static -prof -eventlog -H32m -O -Wall -this-unit-id ghc-heap-8.5 -hide-all-packages -i -ilibraries/ghc-heap/. -ilibraries/gh c-heap/dist-install/build -Ilibraries/ghc-heap/dist-install/build -ilibraries/ghc-heap/dist-install/build/./autogen -Ilibraries/ghc-heap/dist-install/build/./autogen -Ilibraries/ghc-heap/. -optP-include -optPlibraries/ghc-heap/dist-install/build/./autogen/cabal_macros.h -package-id base-4.12.0.0 -package-id ghc-prim-0.5.3 -package-id rts -Wall -XHaskell2010 -O2 -no-user-packa ge-db -rtsopts -Wno-deprecated-flags -Wnoncanonical-monad-instances -odir libraries/ghc-heap/dist-install/build -hidir libraries/ghc-heap/dist-install/build -stubdir libraries/ghc-heap/ dist-install/build -split-sections -c libraries/ghc-heap/./GHC/Exts/Heap/Closures.hs -o libraries/ghc-heap/dist-install/build/GHC/Exts/Heap/Closures.p_o -dyno libraries/ghc-heap/dist-instal l/build/GHC/Exts/Heap/Closures.dyn_o libraries/ghc-heap/GHC/Exts/Heap/Closures.hs:23:1: error: Could not find module `GHC.Exts.Heap.InfoTableProf' It is a member of the hidden package `ghc-heap-8.5'. You can run `:set -package ghc-heap' to expose it. (Note: this unloads all the modules in the current scope.) Use -v to see a list of the files searched for. | 23 | import GHC.Exts.Heap.InfoTableProf | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ make[1]: *** [libraries/ghc-heap/ghc.mk:4: libraries/ghc-heap/dist-install/build/GHC/Exts/Heap/Closures.p_o] Error 1 make: *** [Makefile:127: all] Error 2 For reference, here's my shell.nix: { nixpkgs ? import <nixpkgs> {}, compiler ? "ghcHEAD" }: let inherit (nixpkgs) pkgs; ghc = pkgs.haskell.packages.${compiler}.ghc; in with nixpkgs; lib.overrideDerivation ghc (drv: { name = "ghc-dev"; nativeBuildInputs = drv.nativeBuildInputs ++ [ arcanist git python36Packages.sphinx texlive.combined.scheme-basic ]; }) Any help would be appreciated. Thanks Sean G