Why `sudo -v` prompts for password when sudo doesn't require it?

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http://unix.stackexchange.com – I've set up sudo not to prompt for password by editing the sudoers file: myuser ALL=(ALL:ALL) NOPASSWD: ALL And it works fine, running sudo with no password prompting. But when entering sudo -v I noticed that it prompted for password, only once. I know what sudo -v does, from the manual: If given the -v (validate) option, sudo will update the user's time stamp, prompting for the user's password if necessary. This extends the sudo timeout for another 15 minutes (or whatever the timeout is set to in sudoers) but does not run a command. And I know I don't need to use it anyway (or (HowTos)