Ata' bin al-Sa'ib narrated from several students of Sayyiduna Abdullah (may Allah be pleased with him): Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) used to say: When someone performs the witr and then sleeps, and then wakes up, he should cancel his previous witr and join another rak'ah to it, then after that (after completing his voluntary prayers) he should perform the witr.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Kabir; the narrator Ata' bin al-Sa'ib has been criticised on account of his ikhtilat (memory deterioration).