QPainter drawRect() fills rotated and scaled rectangles incorrectly

QPainter draws the fill of rectangles incorrectly if the QPainter coordinate system has been rotated 45 degrees and scaled. The stroke of the rectangle is drawn correctly, but the fill area is oversized. This only happens in 45 degrees, other angles are drawn correctly. Here's a code clip, while there is an attachment with full example.

QPainter p(this);
p.rotate(45);
p.scale(2, 1);
p.setBrush(Qt::red);
p.drawRect(50, 0, 100, 50);

The attached picture shows the result. The red rectangle is drawn with rotation of 45 degrees. The green rectangle is drawn with rotation of 45.0001 degrees.

The workaround is to rotate by 45.0001 degrees. Also, fillRect() works correctly. However, fillRect() can't be used when rounded rectangles are needed. In that case, one needs to call drawRoundedRect(), which also has this bug.

The bug can be seen in Mac with the latest Git stable version. It is also present in the Ubuntu Qt 5.0.2 version. I think I saw this bug in Qt 4.8, too.