QT compile error: endl will always evaluate to true

QT compile error: endl will always evaluate to true

I have the following code snippet that compiles
QByteArray block;
QDataStream out(&block, QIODevice::WriteOnly);
for (QStringList::Iterator it = commandList.begin(); it !=
commandList.end(); ++it) {
out << "Command: " << *it << endl;
}
but always gives me this warning:
test.cpp:87: warning: the address of 'QTextStream& endl(QTextStream&)'
will always evaluate as 'true' [-Waddress]
What does it mean and how do I fix it? Since a newline character is
printing I assume this is not a namespace issue...