DRIVERS-1251: Spec change: https://github.com/mongodb/specifications/commit/6c5b2acbf5a30b2c79e904532d51ba9ed8783247#diff-f9e2401b2bae6b166a6909f98c79f8fef65989037feea8d1cc1416543a57eb55
See DRIVERS-1251 for updated details.
PR