Java Synth: can't get a white background in textfield

I can't get a white background for my JTextField, what am I doing wrong ? (I know that the image is not painted in the center for the text to be shown, but I'va set background to white; has no effect)

-- XML --

<synth>
    <style id="textfield">
        <state>
            <font name="Verdana" size="12" />
            <color value="black" type="TEXT_FOREGROUND" />
            <color value="white" type="TEXT_BACKGROUND" />
            <color value="white" type="BACKGROUND" />
        </state>
        <imagePainter method="textFieldBorder" path="images/ch_textfield.png"
            sourceInsets="4 6 4 6" paintCenter="false" />
        <insets top="4" left="6" bottom="4" right="6" />
    </style>
    <bind style="textfield" type="region" key="TextField" />
</synth>

-- Java --

public class SynthCh extends JApplet {
    public void init() {
        try {
            initLookAndFeel();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        setSize(300, 50);
        initUi();
    }
    public void initUi() {
        JPanel jpMain = new JPanel();
        jpMain.setName("Root");
        JTextField textField = new JTextField(10);
        jpMain.setLayout(new FlowLayout());
        this.add(jpMain);
        jpMain.add(textField, BorderLayout.NORTH);
    }
    public static void initLookAndFeel() {
        SynthLookAndFeel lookAndFeel = new SynthLookAndFeel();
        try {
            lookAndFeel.load(SynthCh.class.getResourceAsStream("synthCh.xml"),
                                    SynthCh.class);
            UIManager.setLookAndFeel(lookAndFeel);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

A background cannot be rendered on components that are transparent by default.
Add <opaque value="TRUE"/> at the beginning of your style.