No, bash, I don’t have any mail

Since some time earlier in the Summer, I’ve noticed this appearing a lot in a shells: You have mail in /var/mail/… You have mail in /home/…/Mail/… You have mail in /home/…/Mail/…/… and so on, yet when there really is new mail, the message is correct. I’ve filed it as bug #551487, but I can’t help…