nix-deploy is unusable under non privileged user

[misuzu]

$ nix-deploy system --to remote-server --path $(nix-build --no-out-link -A system deploy.nix)
Generating RSA private key, 2048 bit long modulus
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e is 65537 (0x10001)
writing RSA key
[+] Downloading: /etc/nix/signing-key.sec
nix-deploy: /etc/nix/signing-key.sec: openBinaryFile: does not exist (No such file or directory)
$ ls /etc/nix
nix.conf
$ ssh remote-server ls /etc/nix
nix.conf
signing-key.pub
signing-key.sec
$ sudo nix-store --generate-binary-cache-key localhost /etc/nix/signing-key.sec /etc/nix/signing-key.pub
$ ls /etc/nix
nix.conf  signing-key.pub  signing-key.sec
$ nix-deploy system --to remote-server --path $(nix-build --no-out-link -A system deploy.nix)
[+] Downloading: /etc/nix/signing-key.sec
nix-deploy: /etc/nix/signing-key.sec: openBinaryFile: permission denied (Permission denied)