Widgets-based QFileDialog does not display files matching *.txt when setting mime type to "text/plain"

#include <QApplication>
#include <QFileDialog>
#include <QMimeDatabase>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QFileDialog fileDialog(0, "Open File...");
    fileDialog.setOption(QFileDialog::DontUseNativeDialog);
    fileDialog.setAcceptMode(QFileDialog::AcceptOpen);
    fileDialog.setFileMode(QFileDialog::ExistingFile);
    fileDialog.setMimeTypeFilters(QStringList() << "text/plain"<< "text/html");
    fileDialog.exec();
    qDebug() << QT_VERSION_STR << fileDialog.selectedFiles();
    return 0;
}