This is a kind of quirky way of achieving it, but it worked for me.
Having frame-title-format set to its original value:
(setq frame-title-format '(multiple-frames "%b"
("" invocation-name "@" system-name)))
shows this on wmctrl utility to interact with X-Windows manager:
$ wmctrl -l
0x00e00003 0 ES-00002604 /...