Error running on darwin aarch64 related to with-utf8_1_1_0_0

[Masrepus]

On the current nixos-unstable branch (as of May 12: NixOS/nixpkgs@d89fc19), I consistently get this error when trying to run nix-index on an aarch64 MacBook:

+ querying available packages
error: querying available packages failed
caused by: nix-env failed with error: nix-env failed with exit status: 1:
warning: Nix search path entry '/nix/var/nix/profiles/per-user/root/channels' does not exist, ignoring
error:
       … while evaluating the attribute 'with-utf8_1_1_0_0'
         at /nix/store/ccfwxygjrarahgfv5865x2f828sjr5h0-source/pkgs/development/haskell-modules/configuration-darwin.nix:65:5:
           64|     with-utf8 = addExtraLibrary pkgs.libiconv super.with-utf8;
           65|     with-utf8_1_1_0_0 = addExtraLibrary pkgs.libiconv super.with-utf8_1_1_0_0;
             |     ^
           66|

       … in the left operand of the update (//) operator
         at /nix/store/ccfwxygjrarahgfv5865x2f828sjr5h0-source/pkgs/development/haskell-modules/lib/compose.nix:48:5:
           47|     ))
           48|     // {
             |     ^
           49|       overrideScope = scope: overrideCabal f (drv.overrideScope scope);

       error: attribute 'with-utf8_1_1_0_0' missing
       at /nix/store/ccfwxygjrarahgfv5865x2f828sjr5h0-source/pkgs/development/haskell-modules/configuration-darwin.nix:65:55:
           64|     with-utf8 = addExtraLibrary pkgs.libiconv super.with-utf8;
           65|     with-utf8_1_1_0_0 = addExtraLibrary pkgs.libiconv super.with-utf8_1_1_0_0;
             |                                                       ^
           66|

Not sure if it's something in nix-index or generally in nixpkgs, but I haven't found any related issue in either repo yet.