As the mistake was carried out through the god Indra, he grants Hanuman a want that his system would be as sturdy as Indra's Vajra, Which his Vajra can also not harm him. Coupled with Indra other gods have also granted him needs: the God Agni granted Hanuman a wish https://vashikarantotke45212.digitollblog.com/36831422/about-hanuman