First Item in ListView with sections fails to update layout

import QtQuick 2.0

Rectangle {
    id: mainWindow
    width: 800
    height: 600

    ListModel {
        id: lm
        ListElement {
            category: "Human Players"
            name: "Player 1"
        }
        ListElement {
            category: "Human Players"
            name: "Player 2"
        }
        ListElement {
            category: "AI Players"
            name: "AI 1"
        }
        ListElement {
            category: "AI Players"
            name: "AI 2"
        }
    }

    ListView {
        model: lm
        delegate: Text {
            text: name
            font.pixelSize: 20 * (mainWindow.height / 600)
        }
        section.property: "category"
        section.delegate: Text {
            text: section
            font.pixelSize: 40 * (mainWindow.height / 600)
        }
        anchors.fill: parent
    }
}