Temporarily using an updated version of nix isn't working

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1

The nix version on my system is nix (Nix) 2.24.12. This version suffers from this horrible error message that I noticed has been patched out in newer versions of nix.
error: illegal path references in fixed-output derivation

However, I have tried to use the master branch of nix

$ nix --version
nix (Nix) 2.27.0pre20250311_8e8edb5

In the following ways:

  • nix build, then use by result/bin/nix ...
  • nix shell .#packages.x86_64-linux.default and then run nix normally

Both of these still give me the old error message instead of the updated one. How can this be?