QPainter::drawText() does not change a bounding rect of the QPicture

If I draw a text over QPicture object with QPainter::drawText() the size of the QPicture object does not change.
Here is a small example:

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QPicture canvas;
QPainter painter;

painter.begin(&canvas);
painter.drawRect(10, 10, 100, 100);
painter.end();
qDebug() << canvas.boundingRect();

painter.begin(&canvas);
painter.drawRect(10, 10, 100, 100);
painter.drawText(10, 10, "Long text outside of the box");
painter.end();
qDebug() << canvas.boundingRect();
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