Semi-transparent box around QPixmap PNG that has transparency

[minorsecond]

I'm trying to display a png that has a transparent background in a label in a dialog box. Here is my code:

About::About(QWidget *parent) {
    /*
     * About app dialog
     */

    ui.setupUi(this);
    this->setFixedSize(230, 252);
    QPixmap pixmap("../Resources/mini-icon.png");
    ui.miniIcon->setPixmap(pixmap);
    ui.miniIcon->repaint();
}

This dialog window displays correctly, but there is a barely discernible box around the png (shown below). I've verified that the png is indeed transparent in Photoshop. The dimensions of the semi-transparent box are the same as that of the image file. Have I missed a step?