How to change the title of the root window?

I'm trying to get started with ltk and of cause running into many problems. One is: how do I change the title of the root window (it is "LTK" as default).

The corresponding python code would be:

root = Tk() root.title("Hello, world")

This was one of my many unsuccessful tries:

(defun how-to-set-title ()   (ltk:with-ltk ()     (let* ((root (make-instance 'ltk:widget :name "." :path "."))            (b (make-instance 'button                              :master nil                              :text "Press Me"                              :command (lambda ()                                         (format t "Hello World!~&")))))       (setf (title root) "My app")       (pack b))))

I experienced a bit with toplevel (where I could set the name of the window) but this always opened an additional new window.

Any help appreciated!

Regards Volker