 On 13 October 1837, conscious that he had not long to live, Yohannan designated as coadjutor and 'guardian of the throne' Gregory Peter di Natale, metropolitan of Gazarta, presumably with the intention of excluding his nephew Eliya from the patriarchal dignity.However, he did not promise the succession to his coadjutor, and in order to ensure that the hereditary principle would play no part in the selection of the next patriarch the Vatican appointed by a bull of 25 September 1838 Nicholas Zaya, metropolitan of Salmas, Yohannan's coadjutor with the right of succession.The reason given in the bull for this decision was the growing infirmity of the patriarch and the desirability of avoiding inconvenience and harm should the patriarchate suddenly become vacant.