QFileIconProvider: available sizes only up to 32x32?

[sedi]

Hi,
I am using the QFileIconProvider this way:

QFileInfo info = QFileInfo(myFileName);
QFileIconProvider provider;
QIcon icon = provider.icon(info);
qDebug()<<"availableSizes: "<<icon.availableSizes();

QFileInfo info = QFileInfo(myFileName);
QFileIconProvider provider;
QIcon icon = provider.icon(info);
qDebug()<<"availableSizes: "<<icon.availableSizes();

To copy to clipboard, switch view to plain text mode 

(truth be told I am actually meddling around with the SimpleFileBrowser example, so inside the requestPixmap() method I use the m_provider member variable instead of defining the provider for each file)

But, regardless of which file I examine with this, I always get

availableSizes: (QSize(16, 16), QSize(32, 32))

as the only available resolutions. Is it actually true, that there are no larger Icons available or am I doing something wong?
(Windows 10, Qt 5.7.1, MinGw 5.3.0)

Any idea on how to access larger icons?
I've searched around in vain, there also doesn't seem to be an open QtBug in relation with 5.7.x and QFileIconProvider.
What am I missing?