Following the death of al-Mu'tasim in January 842, Ishaq administered the oath of allegiance in Baghdad for his son al-Wathiq (r. 842–847).[15] Under the new caliph, he was called to preside over the cases of several mazalim officials during a general crackdown against the government bureaucracy in 843-4, and in 845 he oversaw the events of the festive season (mawsim) during the annual pilgrimage.[16] That same year he was, according to al-Suli and al-Shabushti, assigned the governorship of Khurasan following the death of 'Abdallah ibn Tahir, but al-Wathiq subsequently changed his mind and canceled the appointment, giving Khurasan to 'Abdallah's son Tahir instead.[17]