GtkListBox children size?

[The Devils Jester <thedevilsjester gmail com>]

I am trying to use the GtkListBox widget, and when I add a child widget to
the list using the code below, I get a new list entry for each label I add,
but the list entry is only a few pixels in height, and it doesnt appear to
show the actual child widget (just a few pixels of the selection rectangle).

    GtkWidget* widget = gtk_list_box_new ();
    ...add widget to parent...
    GtkWidget* lbl = gtk_label_new(text.c_str());
    gtk_container_add(GTK_CONTAINER(widget), lbl);

Am I doing something wrong?