Wrong background for transient scrollbars

#include <QtWidgets>

class ProxyStyle : public QProxyStyle
{
public:
    ProxyStyle() : QProxyStyle(QStyleFactory::create("fusion")) { }
    int styleHint(StyleHint h, const QStyleOption *o = 0, const QWidget *w = 0, QStyleHintReturn *d = 0) const
    {
        if (h == QStyle::SH_ScrollBar_Transient)
            return 1;
        return QProxyStyle::styleHint(h, o, w, d);
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
#ifndef Q_OS_MAC
    app.setStyle(new ProxyStyle);
#endif
    QTextEdit ta;
    ta.setStyleSheet("QTextEdit { color: #eee; background: #333; }");
    for (int i = 0; i < 200; ++i)
        ta.append(QString::number(i));
    ta.show();
    return app.exec();
}