FAIL: nixos-generate --system aarch64 -f sd-aarch64

Following the instructions here I added this to my build host’s configuration.nix:

  boot.binfmt.emulatedSystems = [ "aarch64-linux" ];

And I tried to build my current config into an image, this failed with the ambiguous error.

However, even a generic generate without a specified conf fails with error: Target specification with 1 components is ambiguous:

nixos-generate --system aarch64 -f sd-aarch64
       … while calling the 'seq' builtin

         at /nix/store/990lzihr3amscp9df21spc8khdbn4ml6-nixos-23.11/nixos/lib/modules.nix:320:18:

          319|         options = checked options;
          320|         config = checked (removeAttrs config [ "_module" ]);
             |                  ^
          321|         _module = checked (config._module);

       … while evaluating a branch condition

         at /nix/store/990lzihr3amscp9df21spc8khdbn4ml6-nixos-23.11/nixos/lib/modules.nix:261:9:

          260|       checkUnmatched =
          261|         if config._module.check && config._module.freeformType == null && merged.unmatchedDefns != [] then
             |         ^
          262|           let

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: Target specification with 1 components is ambiguous

Am I missing another step in the cross-compilation setup?