Can't change NPC's skin in Paper 1.8.8

[HanSiqi2008]

Server Software

Paper 1.8.8 445

Problem

I tried run command /znpcs skin 3 https://s.namemc.com/i/bb32e8be177bf74b.png and /znpcs -id 3 -skin https://s.namemc.com/i/bb32e8be177bf74b.png and get an error

but in wiki and spigotmc, the command is theoretically no error.