JavaFX 2.0 :: TreeTable Can't Change Title

I change TreeTableColumn.text but I got a Exception
 
Exception in thread "JavaFX Application Thread" java.lang.ClassCastException:
javafx.scene.control.TreeTableColumn cannot be cast to javafx.scene.control.TableColumn
    at com.sun.javafx.scene.control.skin.TableHeaderRow$10.invalidated(TableHeaderRow.java:277)

so I check TableHeaderRow . I find this method
 
private final InvalidationListener columnTextListener = new InvalidationListener() {
        @Override public void invalidated(Observable observable) {
            TableColumn<?,?> column = (TableColumn<?,?>) ((StringProperty)observable).getBean();
            CheckMenuItem menuItem = columnMenuItems.get(column);
            if (menuItem != null) {
                menuItem.setText(getText(column.getText(), column));
            }
        }
    };

why don't they use this

TableColumnBase<?,?> column = (TableColumnBase<?,?>) ((StringProperty)observable).getBean();