bxSlider broken window handlers

HTML

<script src="https://rawgit.com/stevenwanderski/bxslider-4/master/dist/jquery.bxslider.js"></script>
<button type="button" class="enable">Enable slideshow</button>
<button type="button" class="disable">Disable slideshow</button>
<ul class="bxslider">
  <li><img src="https://placeimg.com/640/480/animals" title="Funky roots" /></li>
  <li><img src="https://placeimg.com/640/480/nature" title="The long and winding road" /></li>
  <li><img src="https://placeimg.com/640/480/tech" title="Happy trees" /></li>
</ul>

JavaScript

$(document).ready(function(){
  let slider = $('.bxslider').bxSlider()
  let enableSlideshowBtn = $('.enable');
	let disableSlideshowBtn = $('.disable');

  enableSlideshowBtn.on('click', function() {
    slider.reloadSlider({
      auto: true
    });
  });

  disableSlideshowBtn.on('click', function() {
    slider.reloadSlider({
      auto: false
    });
  });
});