qmllint: property types not recognized when doing type conversion

import QtQuick 2.0

Text {
    id: root;
    property int number: 0
    text: root.number.toString()
}

$ qmllint -U test.qml 
Warning: Type "int" of member "number" not found at 6:16.
    text: root.number.toString()

Text { 
    id: root
    property double value: 0
    text: root.value.toFixed(3) 
}