It isn't possible to manually set QFileDialog as QFileDialog::getExistingDirectory

While tweaking an instance of QFileDialog on a pet project of mine I've noticed that although QFileDialog::getExistingDirectory() works as expected, the following code generates a regular file dialog, which does not filter out regular files:

<code>
QFileDialog fd(this, tr("Select base directory"), base_dir);
bool validatePage();
fd.setFileMode(QFileDialog::Directory);
fd.setOptions(QFileDialog::ShowDirsOnly);
fd.setViewMode(QFileDialog::List);
fd.exec();
</code>