How do I stop the column headings of a GtkCList disappearing when the list is scrolled?

This happens when a GtkCList is packed into a GtkScrolledWindow using the function gtk_scroll_window_add_with_viewport(). The prefered method of adding a CList to a scrolled window is to use the function gtk_container_add, as in:

    GtkWidget *scrolled, *clist;
    char *titles[] = { "Title1" , "Title2" };

    scrolled = gtk_scrolled_window_new(NULL, NULL);

    clist = gtk_clist_new_with_titles(2, titles);
    gtk_container_add(GTK_CONTAINER(scrolled), clist);