As The error was performed by the god Indra, he grants Hanuman a want that his human body could be as powerful as Indra's Vajra, Which his Vajra also can not damage him. Coupled with Indra other gods have also granted him needs: the God Agni granted Hanuman a wish https://www.diigo.com/item/note/avyq4/182s?k=a383985d376117bfd69311ed4c19ce87