Qt5 app doesn't showing correct palette

[Guest]

Hey there,
I'm currently porting my Qt app from Qt4 to Qt5. Compiling works fine, but my app now looks different.
Here's a small example of my problem. The output of qDebug(...) is with Qt4 and Qt5 the same, both: RGB (255,0,0) but the shadow is not visible if i compile it with Qt5.
I'm using openSUSE with KDE desktop. I also tried it on icewm. There the same problem appears.
Does anyone know this problem?

@#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QCheckBox>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

QPalette palette;

palette.setBrush(QPalette::Shadow, QBrush(Qt::red, Qt::SolidPattern));

ui->checkBox->setPalette(palette);

QColor color = ui->checkBox->palette().shadow().color();
qDebug("palette: RGB(%i,%i,%i)", color.red(), color.green(), color.blue());

}

MainWindow::~MainWindow()
{
delete ui;
}@