Swapspace option not properly configured out of box?

When I set services.swapspace.enable to true in my configuration.nix, the swapspace daemon starts, but nothing happens. When I run swapspace --inspect, it returns:

Error: Could not get filesystem information for swap directory '/nix/store/sagyf11l27503hidpz6vy0iwgqwgis0n-swapspace-1.18.1/var/lib/swapspace': No such file or directory
The filesystem holding swapspace's swap directory isn't big enough to hold useful swapfiles.
Please try to expand this partition or relocate it to a larger one, if possible; or if all else fails, choose a different swap directory in your swapspace configuration.

I am not sure how to solve this problem, if I set a different swap path in the config, it just goes to /<nix store path>/<configured path>.

Could be a bug in the module or package (or even upstream) if it’s not reading swappath as an absolute path despite leading /. I’d report in nixpkgs in any case.