Gpg: Delete passphrase from gpg-agent

Problem

Gpg-agent has stored my passphrase. How can I make gpg ask for my passphrase again?

Send a SIGHUP signal to the gpg-agent process. This will clear all stored passphrases.

pkill -SIGHUP gpg-agent

How to tell the gpg agent to forget a passphrase: Same question - with answer - on Gnupg-users mailing list