Transparent QQuickWidget: Rectangle antialising=true results in edges standing out

Qml Rectangle with antialiasing doesn't seem to take the actual background properly into account if displayed in a transparent QQuickWidget stacked on the top. This is clearly visible with very light colors since a lot of dark pixels are drawn around the edges of Rectangle in worst cases making the edges really stand out.

This problem does not occur if the QQuickWidget is not transparent. The problem disappears when antialiasing property is set to false.

Steps to reproduce:

1. Run the attached project
2. Click "Toggle antialiasing"