QtQuick.Particles GPU usage issue

slow.qml

import QtQuick 2.0
import QtQuick.Particles 2.0

Item {
  width: 1500
  height: 800
  Rectangle {
    color: 'black'
    anchors.fill: parent
  }
  ParticleSystem {
    id: system
    anchors.fill: parent

    Emitter {
      id: emitter
      enabled: false
      emitRate: 1
      lifeSpan: 2000
      size: 24
      sizeVariation: 16
      velocity: AngleDirection {angleVariation: 180; magnitude: 150; magnitudeVariation: 260}
      acceleration: AngleDirection {angleVariation: 180; magnitude: 0; magnitudeVariation: 60}
    }

    function boom(count) {
      visible = true;
      emitter.enabled = true;
      emitter.burst(count);
      emitter.enabled = false;
    }

    // GPU is being eaten like crazy even if this line is commented out
    Component.onCompleted: boom(100)

    ItemParticle {
      delegate: Rectangle {
        color: 'red'
        width: 4
        height: 4
      }
    }
  }
}