gksu not working after upgrade to debian buster

There are a few icons on my (xfce4) desktop that use gksu, for example a root terminal. They used to work fine in debian stretch. Now, gksu asks for the root password (once, it manages to save it for the session), but then fails to start the terminal (there is a flash of a window being created and closed immediately, but I cannot make out what it would contain). When running in a terminal, the output is the following: :~$ gksu /usr/bin/x-terminal-emulator # posix_spawn avoided (fd close requested) # Failed to use specified server: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.67 was not provided by any .service files # Falling back to default server. # posix_spawn avoided (fd close requested) # watch_fast: "/org/gnome/terminal/legacy/" (establishing: 0, active: 0) # unwatch_fast: "/org/gnome/terminal/legacy/" (active: 0, establishing: 1) # watch_established: "/org/gnome/terminal/legacy/" (establishing: 0) gksudo does work, although it erroneously prompts for the root password, but expects the user password. Google did not find me relevant hits about "gksu" debian buster error "Failed to use specified server: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name" :1.67 was not provided by any .service files and some variants. Can anyone suggest a fix for this?