QQmlPropertyMap::valueChanged not emitted

In some cases a signal QQmlPropertyMap::valueChanged is not emitted.

The map is exposed to qml as a property _Q_PROPERTY(QQmlPropertyMap* event_levels READ getEventLevelsQml);_

When assigning a value to a key convertable to integer from 0 to aprox. 4000000000 the signal is not emitted.                                   

For ex.
settingsModel.event_levels["4000000000"] = "asdf";

settingsModel.event_levels["1234"] = "asdf";

settingsModel.event_levels["0"] = "asdf";

When using slightly different keys with a leading zero or letters the signal is emitted.

For ex.

settingsModel.event_levels["1234sdf"] = "asdf";
settingsModel.event_levels["01234"] = "asdf";
settingsModel.event_levels["-1"] = "asdf";
settingsModel.event_levels["1234.1234"] = "asdf";