Why does insertBefore not work when put in the if statement?

          ul.insertBefore(li, prevLi);
           ``` 
But when I add the rest of it, all the Up buttons stop working and the remove one still works. I was coding in VSC and thought it might be that but even in Workspace it's wrong. I just can't seem to see it. Clearly there's an issue with the first part of the event listener, but I'll include the whole one, in case.  Thanks.

if (event.target.className == 'remove'){
  let li = event.target.parentNode;
  let ul = li.parentNode;
  ul.removeChild(li);
}

  <input type = "text" class = "description">
  <button class = "description">Change List Description </button>



  <ul>
    <li>grapes <button class = "up">Up</button>
      <button class = "down">Down</button>
      <button class = "remove">Remove</button>
    </li>
    <li>amethyst <button class = "up">Up</button>
      <button class = "down">Down</button>
      <button class = "remove">Remove</button>
    </li>
    <li>lavender <button class = "up">Up</button>
      <button class = "down">Down</button>
      <button class = "remove">Remove</button>
    </li>
    <li>plums<button class = "up">Up</button>
      <button class = "down">Down</button>
      <button class = "remove">Remove</button>
    </li>
  </ul>