ListView horizontal scrolling makes the view go outside bounds

import QtQuick 2.7
import QtQuick.Window 2.2

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

   ListView {
       id: listView
       anchors.fill: parent
       model: 100
       spacing: 5
       delegate: Rectangle {
           border.width: 3
           border.color: "black"
           width: listView.width + 300
           height: 80
       }
       flickableDirection: Flickable.HorizontalAndVerticalFlick
   }
}