Cannot suspend: Failed to lock the screen

Hey folks,

I've recently upgraded from Fedora 33 to Fedora 35 with Xfce 4.16 (xfce4-session 4.16.0).

When I attempt to suspend the computer via the Log out screen or via command line, I cannot.

I see a popup window that either says Failed to lock the screen or Received error while trying to log out GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Type of message, "(yb)", does not match expected type "(b").

The terminal output is:

Received error while trying to log out, error was GDBus.Error:org.xfce.SessionManager.Error.Failed: Failed to lock the screen.

My lock command is slock via:

xfconf-query -c xfce4-session -p /general/LockCommand -s slock

Running plain slock works. When I disable screen locking on suspend, I can successfully suspend.

I was searching the error and found:

• https://linux.debian.user.narkive.com/X61Di2Dy/some-recent-update-to-unstable-seems-to-have-broken-xfce4-for-me
• https://unix.stackexchange.com/questions/626284/thunar-bug-should-i-report-to-xfce-or-ubuntu
• https://askubuntu.com/questions/1233288/unable-to-logout-from-guest-session-on-xubuntu-20-04
• https://bugzilla.redhat.com/show_bug.cgi?id=1729059
• https://forums.freebsd.org/threads/xfce-wont-let-me-log-out-anymore.76968/
• https://www.reddit.com/r/xfce/comments/bej4xx/received_error_while_trying_to_log_out/
• https://www.mail-archive.com/debian-xfce@lists.debian.org/msg02042.html
• https://forum.xfce.org/viewtopic.php?id=14993338791

But no luck figuring out how to fix this. Is it possible that this is a bug/regression in 4.16?

Thanks for help