Windows: TextField's placeholder text is blurry and almost transparent when you set transparent color on QQuickWindow

#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QtQuick2ApplicationViewer viewer;

    viewer.setColor(QColor(Qt::transparent)); //BUG with placeholder. If you comment this line, the placeholder is okay.
    viewer.setFlags(Qt::FramelessWindowHint
                     | Qt::WindowSystemMenuHint
                     | Qt::WindowMinimizeButtonHint
                     | Qt::Window);

    viewer.setMainQmlFile(QStringLiteral("qml/BugTextfieldPlaceholder/main.qml"));
    viewer.showExpanded();

    return app.exec();
}

import QtQuick 2.0
import QtQuick.Controls 1.0

Rectangle {
    width: 360
    height: 360
    color: "lightblue"
    border.color: "grey"
    border.width: 2
    radius: 15

    Text {
        x: 20; y: 20; width: 60; height: 30;
        text: "QUIT"
        MouseArea {
            anchors.fill: parent
            onClicked: {
                Qt.quit();
            }
            cursorShape: Qt.PointingHandCursor
        }
    }

    TextField {
        placeholderText: "PLACEHOLDER"
        x: 80; y: 100; width: 250; height: 50;
        font.pixelSize: 25
    }

}