Is the prostration of forgetfulness (sujud al-sahw) performed in a two-rak'ah prayer?

The prostration of forgetfulness (Sujud al-Sahw) is legislated for all prayers, whether obligatory (fard) or supererogatory (nafl), regardless of the number of their rak'ahs. The proof for this is the hadith narrated by Ibn Mas'ud (may Allah be pleased with him) that the Prophet (peace be upon him) prayed five rak'ahs, then prostrated the two prostrations of forgetfulness and said: "Indeed, I am only a human being like you; I forget as you forget." ... "So if one of you forgets, he should prostrate two prostrations." Ibn Qudamah mentioned that the ruling for supererogatory prayers concerning the prostration of forgetfulness is the same as the ruling for obligatory prayers, and this is the view of the generality of the people of knowledge. There is no one who differs from this except Ibn Sirin, and his view contradicts the generality of the Prophet's (peace be upon him) statement.