Applying QGraphicsBlurEffect to widgets embedded in QGraphicsView makes it disappear

When creating a QPushButton and placing it in a QGraphicsScene, then applying a QGraphicsBlurEffect to the button, the button disappears as soon as the blurRadius != 0.

QPushButton *blurButton = new QPushButton("Blur");
QGraphicsProxyWidget *blurItem = scene->addWidget(blurButton);
blurItem->setPos(blurButton>width()/2, 10-blurButton>height());
QGraphicsBlurEffect *blurEffect = new QGraphicsBlurEffect(this);
blurEffect->setBlurRadius(0);
blurButton->setGraphicsEffect(blurEffect);

However, changing the graphics effect to apply to the QGraphicsProxyWidget fixes the problem:

blurItem->setGraphicsEffect(blurEffect);