super() compiled incorrectly inside class expression

This fails:

// input
SubClass = class extends SuperClass {
  constructor() {
    super();
  }
}

// output
SubClass = (function (SuperClass) {
  function SubClass() {
    undefined.prototype();
  }

  SubClass.prototype = Object.create( SuperClass && SuperClass.prototype );
  SubClass.prototype.constructor = SubClass;

  return SubClass;
}(SuperClass))

Works fine with a class declaration.