qmlint: type qlonglong (qint64) not found

class TestClass : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    QML_SINGLETON
    Q_PROPERTY(qint64 ...)
}

Warning: main.qml:23:23: Type "qlonglong" of property "importantNumber" not found. This is likely due to a missing dependency entry or a type not being exposed declaratively.
      text: TestClass.importantNumber
                      ^^^^^^^^^^^^^^^
Error: main.qml:23:23: Could not compile binding for text: Cannot load property importantNumber from TestClass of TestClass.
      text: TestClass.importantNumber
                      ^^^^^^^^^^^^^^^