Unable to build on NixOS

[Sean D Gillespie]

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