lupdate does not find strings in operator overloading methods

lupdate does not find strings in operator overloading methods. My case is a class (QObject descendant), inside a namespace.

namespace Test
{
class MyClass : public QObject
{
Q_OBJECT

public:
explicit MyClass(QObject *parent = 0) : QObject(parent) { }

void myMethod();

MyClass *operator<<(int i);
};

This is the .cpp file of this class:

/*
TRANSLATOR Test::MyClass
*/

#include <QProgressDialog>

#include "test.h"

using namespace Test;

void MyClass::myMethod()
{
QProgressDialog dialog(tr("Can see this string"),QString(),0,10);

dialog.exec();
}

MyClass *MyClass::operator<<(int i)
{
QProgressDialog dialog(tr("Cannot see this string"),QString(),0,10);

dialog.exec();

return this;
}

The string in "myMethod" is found by lupdate, the one in << operator not.

lupdate reports:

lupdate . -ts lupdate_test.ts
Scanning directory '.'...C:/Qt4Projects/lupdate_bug/test.cpp:20: tr() cannot be
called without context

Updating 'lupdate_test.ts'...
Found 1 source text(s) (1 new and 0 already existing)

Qt 4.5.3 was the latest version (AFAIK) that didn't have this problem.