MSSQL and stored procedure

[savior]

Hi,
How do I read nvarchar (255) output value of the stored procedure:

db = QSqlDatabase::addDatabase("QODBC3");
db.setDatabaseName("Driver={SQL Server};Server=homepc\\SQLEXPRESS;Database=Test_DB;");
db.setUserName("sa");
db.setPassword("sa");
if (!db.open())
{
    qDebug() << "Error";
}else{
    qDebug() << "OK";
}

QVariant strValue(QString(255,' ')); 
int n = 0;

QSqlQuery query;
query.setForwardOnly(true);
QString sqlString = "{CALL test(:Name,:Str,:Number)}";
query.prepare(sqlString);
query.bindValue(":Name","Test");
query.bindValue(":Str", strValue, QSql::Out);
query.bindValue(":Number", n, QSql::Out);
if (!query.exec()) qDebug() << query.lastError().text();
qDebug() << query.boundValue(":Number").toInt();
qDebug() << query.boundValue(":Str").toString();

lasterror return "QODBCResult::exec: Unable to execute statement: "[Microsoft][ODBC SQL Server Driver][SQL Server]Invalid parameter 2 (''): Data type 0x63 is a deprecated large object, or LOB, but is marked as output parameter. Deprecated types are not supported as output parameters. Use current large object types instead."
"[Microsoft][ODBC SQL Server Driver][SQL Server]Invalid parameter 2 (''): Data type 0x63 is a deprecated large object, or LOB, but is marked as output parameter. Deprecated types are not supported as output parameters. Use current large object types instead. QODBC3: Unable to execute statement"

If I set less value for a string size for example QVariant strValue(QString(100,' ')); stored procedure return value, itherwise value is empty.

How to correctly read the value?
Regards

Qt 4.8.2 and raspberry pi [TDS][ODBC]