[ngIRCd-ML] operator command

I am a student worker at a college and learning how to set up ngircd. I have a trouble to log on as IRC operator. I configured an [Oper] section on config file. After I use /OPER command to be an IRC operator, log file says: "Got valid OPER for "Name" from "Nickname!~Name@com", user is an IRC operator now. However, when I use commands such as kick, it says "your privileges are too low". Does anyone have any idea how to fix this? I really appreciate your help. Warmly, Daiki Akiyoshi Earlham College'18