Urwah bin Mas'ud says: I do not mind if the tathwib is being called for the Fajr prayer while I am still reciting my daily portion (wird) and have not yet prayed the Witr.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its narrators are the narrators of the Sahih. Others besides him also gave this fatwa; by that I mean Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him).