headerValues throws an error after addSheet

[konser80]

add sheet with no params
then try to get headerValues
previous version (3.3.0) gives me undefined (it's good)
current version (4.1.1) throws 'Header values are not yet loaded' (that's not good)

  docid.addSheet();
  sheet.updateProperties({ title: sheetname });
  ... 
  const sheet = docid.sheetsByTitle[sheetname];
  const oldheaders = sheet.headerValues;