WTF?

drv.json

{
  "/nix/store/qi84ww9gaac87c6k3r2zigsmvv2lbhsb-initrd.drv": {
    "outputs": {
      "out": {
        "path": "/nix/store/ayipqlik257bg0zs658msyip3vl1kzpq-initrd"
      }
    },
    "inputSrcs": [
      "/nix/store/0q0xx96z8ll2kxzpzbg0cpv1v3h66ig2-make-initrd.sh",
      "/nix/store/rv3s91qgcyl9hmd760dzjbm1x605iq2a-paths-from-graph.pl"
    ],
    "inputDrvs": {
      "/nix/store/4hzxqrr50c5wkzfx334dxr1a25hmn083-stdenv-linux.drv": [
        "out"
      ],
      "/nix/store/7r6lwlfwzmxg9ba49s86rv7ivwzdi8nj-systemd-239.drv": [
        "out"
      ],
      "/nix/store/976k19ias01waf2yw0yilv1mv3rblisq-bash-4.4-p23.drv": [
        "out"
      ],
      "/nix/store/dplixqqi6cjk5iisx6xszi5gy96znk25-cpio-2.12.drv": [
        "out"
      ],
      "/nix/store/fvlpc9x5n2q5h7pi5z6xnl860xphyprn-perl-5.28.1.drv": [
        "out"
      ]
    },
    "platform": "x86_64-linux",
    "builder": "/nix/store/a9i0a06gcs8w9fj9nghsl0b6vvqpzpi4-bash-4.4-p23/bin/bash",
    "args": [
      "-e",
      "/nix/store/0q0xx96z8ll2kxzpzbg0cpv1v3h66ig2-make-initrd.sh"
    ],
    "env": {
      "buildInputs": "",
      "builder": "/nix/store/a9i0a06gcs8w9fj9nghsl0b6vvqpzpi4-bash-4.4-p23/bin/bash",
      "compressor": "gzip -9n",
      "configureFlags": "",
      "depsBuildBuild": "",
      "depsBuildBuildPropagated": "",
      "depsBuildTarget": "",
      "depsBuildTargetPropagated": "",
      "depsHostHost": "",
      "depsHostHostPropagated": "",
      "depsTargetTarget": "",
      "depsTargetTargetPropagated": "",
      "doCheck": "",
      "doInstallCheck": "",
      "exportReferencesGraph": "closure-autovt@.service /nix/store/kinpd6wss80pf2d04jnvvmw25lzkrlbq-systemd-239/example/systemd/system/autovt@.service",
      "makeUInitrd": "",
      "name": "initrd",
      "nativeBuildInputs": "/nix/store/7yf3fh95ljf90nnw6cv70dry5jvqin0l-perl-5.28.1 /nix/store/3zbr31pjbvmzrfyicvb8gmzr9ms5fipd-cpio-2.12",
      "objects": "/nix/store/kinpd6wss80pf2d04jnvvmw25lzkrlbq-systemd-239/example/systemd/system/autovt@.service",
      "out": "/nix/store/ayipqlik257bg0zs658msyip3vl1kzpq-initrd",
      "outputs": "out",
      "pathsFromGraph": "/nix/store/rv3s91qgcyl9hmd760dzjbm1x605iq2a-paths-from-graph.pl",
      "prepend": "",
      "propagatedBuildInputs": "",
      "propagatedNativeBuildInputs": "",
      "stdenv": "/nix/store/9qrxkya37d0ajls3yygy0ry268p805v7-stdenv-linux",
      "strictDeps": "",
      "suffices": "none",
      "symlinks": "/etc/systemd/system/autovt@.service",
      "system": "x86_64-linux"
    }
  }
}

gistfile1.txt

 nix-build repro.nix 
these derivations will be built:
  /nix/store/qi84ww9gaac87c6k3r2zigsmvv2lbhsb-initrd.drv
error: invalid character '@' in name 'closure-autovt@.service'

repro.nix

let pkgs = import <nixpkgs> {};
in
  pkgs.makeInitrd {
    contents = [{
      symlink = "/etc/systemd/system/autovt@.service";
      object = "${pkgs.systemd}/example/systemd/system/autovt@.service";
    }];
  }