observer overwriting form value

[stukennedy]

const observers = {
    category: [
      {
        key: 'value',
        call: ({ change }) => {
          console.log(change.newValue);
        },
      },
    ],
  };
  return new MobxReactForm({ fields, observers }, { plugins, hooks });

When I use an observer it seems to empty the form value, should I be returning something from this function?