QIcon pixmap(...) does not upscale

Imagine a png file with dimensions 64x64 called "icon64.png"

QIcon icon("icon64.png");
QPixmap px = icon.pixmap(QSize(128, 128));
qDebug() << px.size();

The final qDebug will always output "QSize(64, 64)" even though we request 128x128.
( See also attached example.zip )