How to save QVariantMap into QSqlDatabase

Question

I've already got an infrastructure to work with. There is an insert function given with the following signature:

insert(const QString& key, const QVariant& value)

Within the function the QSqlQuery is getting prepared:

QSqlQuery query{mySqlDatabase};
QString sql = "INSERT INTO my_table(key, value) VALUES (:key, :value)"
query.prepare(sql);
query.bindValue(ENC(":key"), key);
query.bindValue(ENC(":value"), value.toString());

if (!query.exec()) {
    const auto error = q2.lastError();
    throw std::exception(QString("failed to insert: %1")).arg(error.text()));
}

This works for all the insertions used so far, but now I'm trying to insert a QVariantMap (which is a typedef for QMap<QString,QVariant>, in fact I'm trying to save QMap<QString,int> type):

insert(g_theKey, QVariant(m_theMap));

Upon query execution I'm receiving the following error:

I was looking for solutions on both the Qt website and here, but haven't found a working solution.