mount.ecryptfs fails with error "[-22] Invalid argument"

[Milan Bouchet-Valat]

Binary package hint: ecryptfs-utils

This occurs when I try mounting manually my Private dir, maybe because the passphrase is wrong:
$ keyctl clear @u
$ mount.ecryptfs ~/.Private/ /mnt/
Unable to find a list of options to parse, defaulting to interactive mount
Passphrase: [XXXX]
Error attempting to evaluate mount options: [-22] Invalid argument

That's a problem I've discovered when trying to recover my broken Private directory. It may come from a bad usage of the tool, but still I don't think this kind of mount errors should happen. That really doesn't help finding out what's really wrong!

ProblemType: Bug
Architecture: i386
Date: Wed Dec 9 11:10:42 2009
DistroRelease: Ubuntu 9.10
Package: ecryptfs-utils 81-0ubuntu3
ProcEnviron:
 LANGUAGE=fr_FR.UTF-8
 PATH=(custom, user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: ecryptfs-utils
Uname: Linux 2.6.32-020632rc8-generic i686