Warning about non-NOTIFYable properties in QML

I have a QML based application in Qt that generates some warnings at runtime:

QDeclarativeExpression: Expression "(function $text() { return pinyin })" depends on non-NOTIFYable properties: hanzi::DictionaryEntry::pinyin

I believe it refers to this class which has some properties with no notifier (because not needed):

#ifndef DICTIONARYENTRY_H
#define DICTIONARYENTRY_H

namespace hanzi {

class DictionaryEntry : public QObject {

    Q_OBJECT

    Q_PROPERTY(QString simplified READ simplified)
    Q_PROPERTY(QString traditional READ traditional)
    Q_PROPERTY(QString pinyin READ pinyin)
    Q_PROPERTY(QString definition READ definition)

public:

    explicit DictionaryEntry(QObject* parent = 0);
    const QString& simplified() const;
    const QString& traditional() const;
    const QString& pinyin() const;
    const QString& rawDefinition() const;
    const QStringList& definitions() const;
    const QString& definition() const;
    void setSimplified(const QString& v);
    void setTraditional(const QString& v);
    void setPinyin(const QString& v);
    void setDefinitions(const QStringList& v);

};

}
#endif // DICTIONARYENTRY_H

Does anybody know why it's showing these warnings, and, if they are not important, is there any way to disable them?