Force update of tarball flake input

Help
1

I have the following flake tarball input

inputs = {
    ...
    code = {
      url = "https://code.visualstudio.com/sha/download?build=insider&os=linux-x64";
      type = "tarball";
      flake = false;
    };
};

And I want to update it, but nix flake update seems to just skip it.
Running nix flake lock --update-input code returns instantly, without apparently doing anything. It doesn’t seem to re-fetch the url of the tarball at all. How does it know that the previously downloaded tarball is up to date?

nix flake lock --update-input code -v --refresh doesn’t improve the situation. I don’t get any additional information in verbose mode.