Creating a custom class attributer in QuillJS

I'm trying to create a custom class attributer in QuillJS. I've got this far:

let config = {
  scope: Parchment.Scope.BLOCK,
};

let MClass = new Parchment.Attributor.Class('mark', 'dom-mark', config);
Quill.register(MClass,true)

But when attempting:

this.quillEditor.format('mark', 'MarkThisHere');

I get:

ERROR TypeError: BlotClass.create is not a function

What am i doing wrong?