Relative flake input files

[mainrs]

I am trying to make nix-portable work with https://github.com/divnix/nosys together. As in the README, my inputs include inputs.systems.url = "path:./flake/systems.nix";

Calling nix develop with my local nix works. Using nix-portable returns the error: error: cannot fetch input 'path:./flake/systems.nix?lastModified=1&narHash=sha256-4UCfLMxAeGNJiUoJIdMQRx%2BI5ivP/b8N5FFJ1xlK3Hg%3D' because it uses a relative path.

Any idea how I can fix this?