Can't bootstrap `master` with 9.0.1 (Could not find module ‘GHC.Bits’)

If I try to build master as of commit (6974c9e4) with GHC 9.0.1 as my bootstrapping compiler, it fails with:

compiler/GHC/Prelude.hs:41:8: error:
    Could not find module ‘GHC.Bits’
    Perhaps you meant
      GHC.Exts (from base-4.15.0.0)
      GHC.List (from base-4.15.0.0)
    Use -v (or `:set -v` in ghci) to see a list of the files searched for.
   |
41 | import GHC.Bits as Bits hiding (shiftL, shiftR)
   |        ^^^^^^^^

On the other hand, this does not happen with GHC 8.10.4 as my bootstrapping compiler. Commit c02ac1bb (Re-export GHC.Bits from GHC.Prelude with custom shift implementation.) is most likely to be relevant here, so cc'ing @AndreasK.