[LightDM] Session-cleanup-script executed on login

[ronald]

Session-cleanup-script executed on login

 I've created a script to back up the user's home directory
on logout by using the session-cleanup-script parameter in lightdm.conf.

Even when an existing user uses a wrong password the session-cleanup-script
of lightdm (1.10.0-ubuntu3amd64) is executed, on a failed login( incorrect
password, please try again)!

Is this expected behaviour?

ubuntu 14.04 LTS (lightdm 1.10.0)

Thanks,
Ronald