QSettings::value("Theme") returns an empty QByteArray if beginGroup has been called

#include <QCoreApplication>
#include <QSettings>
#include <QDebug>
#include <QFile>

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

    const QString settingsFilePath = QString::fromUtf8(APP_SOURCE_DIR) + "/settings.conf";
    if (!QFile::exists(settingsFilePath)) {
        qWarning() << settingsFilePath << "doesn't exist";
        return 1;
    }

    qDebug() << "Found settings file at" << settingsFilePath;

    QSettings settings(settingsFilePath, QSettings::IniFormat);
    settings.beginGroup("Material");
    // This makes it work:
    // qDebug() << "allKeys" << settings.allKeys();

    const QByteArray themeValue = settings.value("Theme").toByteArray();
    qDebug() << "themeValue" << themeValue;

    return 0;
}

[Controls]
Style=ResourceStyle
FallbackStyle=Material

[Material]
Theme=Dark
[Material\Font]