Wallepassphrase Error -32601

Hey there, i was trying to extract my private Keys so i had to unlock my wallet first via walletpassphrase… what i get is:

Method not found (code -32601)

what am i doing wrong?

i did: walletpassphrase < phrase > <600>

seems my phrase has been too…!!! I changed it to something more easy, tried again and i did work… strange though…