Why does launchd bootstap fail with "Bootstrap failed: 5: Input/output error"?

When I try to load a self-created LaunchDaemon using

sudo launchctl bootstrap system /Library/LaunchDaemons/local.setup-network.plist

I get the following error

Bootstrap failed: 5: Input/output error

And I don't know what is wrong. My plist looks like this:

label
        local.setup-network

		ProgramArguments
        
			/Library/Scripts/setup-network.sh
        

    	RunAtLoad

The plist is well formed

# plutil -lint /Library/LaunchDaemons/local.setup-network.plist
/Library/LaunchDaemons/local.setup-network.plist: OK

I checked all file permissions and they all look fine to me. The console application shows no errors either.