QFileInfo::isDir() returns false for directories on mapped network paths

QFileInfo::isDir() returns false if the directory lies on a mapped network drive like U:\myname\temp.

But it works correctly on local drives (e.g.: C:\temp) or absolute network drives (e.g.: \\myserver\myname\temp).

Example:

QFileInfo fi("U:\\myname\\temp");
if (fi.isDir())
{
// --> fi.isDir() returns false, though temp is a directory
...
}