Cannot modify object stored in QSharedPointer in QtScript

#include <QtCore>
#include <QtTest>
#include <QtScript/QScriptEngine>

class SandboxTest : public QObject
{
    Q_OBJECT
    
public:
    SandboxTest();
    
private Q_SLOTS:
    void testCase1();
};

SandboxTest::SandboxTest()
{
}

inline bool evaluateScript(QScriptEngine *scriptEngine, const QScriptProgram &script) {
    scriptEngine->evaluate(script);
    if (scriptEngine->hasUncaughtException()) {
        qWarning() << scriptEngine->uncaughtException().toString() << ":"
                   << scriptEngine->uncaughtExceptionLineNumber() << scriptEngine->uncaughtExceptionBacktrace();
        return false;
    }
    return true;
}

inline bool handleScriptErrors(QScriptEngine *scriptEngine) {
    if (scriptEngine->hasUncaughtException()) {
        qWarning() << scriptEngine->uncaughtException().toString() << ":"
                   << scriptEngine->uncaughtExceptionLineNumber() << scriptEngine->uncaughtExceptionBacktrace();
        return false;
    }
    return true;
}

class Object : public QObject
{
    Q_OBJECT
public:
    Q_PROPERTY(int x READ x WRITE setX)

    Object(int x) : mX(x) {}

    int x() const { return mX; }
    void setX(int x) { mX = x; }
private:
    int mX;
};

Q_DECLARE_METATYPE(QSharedPointer<Object>)

void SandboxTest::testCase1()
{
    qRegisterMetaType<QSharedPointer<Object> >("QSharedPointer<Object>");

    QScriptEngine scriptEngine;

    QScriptProgram script("function blah(object) { print(\"in blah()\"); object.x = 6; }");
    Q_ASSERT(evaluateScript(&scriptEngine, script));

    QSharedPointer<Object> object(new Object(5));
    QVariant objectVariant(QVariant::fromValue(object));
    QVERIFY(objectVariant.isValid());

    QVERIFY(objectVariant.canConvert<QSharedPointer<Object> >());
    QSharedPointer<Object> fromObjectVariant(objectVariant.value<QSharedPointer<Object> >());
    QCOMPARE(fromObjectVariant->x(), 5);

    QScriptValueList args;
    args << scriptEngine.newVariant(objectVariant);

    scriptEngine.globalObject().property("blah").call(scriptEngine.globalObject(), args);

    QVERIFY(handleScriptErrors(&scriptEngine));
    QCOMPARE(object->x(), 6);
}

QTEST_MAIN(SandboxTest)

#include "tst_SandboxTest.moc"