Extra dot appears in top left corner of Fusion style spin box frames with no buttons

#include <QApplication>
#include <QWidget>
#include <QMainWindow>
#include <QVBoxLayout>
#include <QSpinBox>
#include <QDoubleSpinBox>
#include <QAbstractSpinBox>

class Window: public QMainWindow
{
public:
    Window(): widget(new QWidget())
    {
        this->setCentralWidget(widget);
        layout = new QVBoxLayout(widget);

        spinbox = new QSpinBox(widget);
        spinbox->setButtonSymbols(QAbstractSpinBox::ButtonSymbols::NoButtons);
        layout->addWidget(spinbox);

        dspinbox = new QDoubleSpinBox(widget);
        dspinbox->setButtonSymbols(QAbstractSpinBox::ButtonSymbols::NoButtons);
        layout->addWidget(dspinbox);
    }

private:
    QWidget* widget;
    QVBoxLayout* layout;
    QSpinBox* spinbox;
    QDoubleSpinBox* dspinbox;
};


int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Window w;
    w.show();
    a.setStyle("Fusion");
    return a.exec();
}