how to underline the text of a button

[Gezim Hoxha <gezimetc shaw ca>]

Hi all.

I'm really new to GTK+ and I need some help with this.

I have a button like this:
GtkButton *pulse_button
pulse_button = g_object_new (GTK_TYPE_BUTTON, 
                                "label", "_Pulse",
                                "use-underline", TRUE,
                                NULL);

And I want to know why isn't the word "Pulse" underlined in the button
text?

Thanks,
-Gezim