startProcess: posix_spawnp: does not exist (No such file or directory)

I have an interesting case where I'm getting the below error when running a bash program but only when it's run via a systemd unit (running within Nixos). telegram: startProcess: posix_spawnp: does not exist (No such file or directory) If I run this program from the command line locally it works with no issue... What might be the cause of this error? It seems like posix_spawnp is actually a syscall which confuses me (why does the error seem to indicate it's an executable?) The actual script is located here: https://github.com/fabianonline/telegram.sh/blob/master/telegram