QColormap::instance(x).depth() returns always the colordepth of the primary screen on Windows

The following prints twice 32 when run on a dual screen setup, with the primary screen (x = 0) set to 32bpp, and the second screen (x = 1) to 16bpp:

qDebug() << QColormap::instance(0).depth();
qDebug() << QColormap::instance(1).depth();

With the primary screen set to 16bpp and the secondary set to 32bpp it prints twice 16.