WinSCP doesn't pass ssh-key password to PuTTY

After upgrading winscp from 5.19 to 6.3.3 WinSCP doesn't pass the ssh-key password to PuTTY any more.

When opening a connection to a my server WinSCP asks for the SSH key password (as always), after I entered it the connection is established. It is also possible to duplicate the session without entering the password again but if I open a PuTTY session, I have to enter the SSH key password again (for each new PuTTY session I open).
Is there a new setting for that?

Additional info:
It has something to do with PuTTY. I downgraded PuTTY to 0.76 and the auth I correctly passed to PuTTY (no need to enter the password again). Upgrading to 0.81 shows the password prompt for the SSH key again.

See Passphrase is requested when opening a PuTTY session from WinSCP since PuTTY 0.78.