A latecomer prayed with an imam who stood for the fifth rak'ah by mistake; what is required of the latecomer?

The questioner : The questioner says: O Shaykh, an imam prayed 'Asr, then he stood up from the fourth rak'ah for the fifth; what is required of the followers?

The Shaykh : He must follow him. It is obligatory for him to follow him, and in the sixth rak'ah it is for your benefit! ; because of his saying (peace be upon him): . But this following, naturally, we do not envision it except after one of the worshippers behind him fulfills the duty of reminding him; that he says: Subhan Allah! The imam may not notice, and this happens often; at that point, the obligation has fallen off the followers, and the obligation upon them has turned into following him. Is that clear? Is it clear up to here?

The questioner: Yes.

The Shaykh : Now, such an incident occurred during the time of the Prophet (peace and blessings be upon him), but some people have a doubt about it. It was reported in "Sahih al-Bukhari": "That the Prophet (peace and blessings be upon him) prayed the midday prayer with the people for five rak'ahs. When he finished the prayer, they said to him: Did you add to the prayer? He said: . They said to him: You prayed five! So he (peace be upon him) prostrated the two prostrations of forgetfulness, then he said: . It is as if the Messenger (peace be upon him) was saying to them: Since you noticed that I added a rak'ah, your first notice should have been for you to remind me, and obviously, reminding the imam is only done by saying Subhan Allah; as he (peace be upon him) said: - or as he (peace be upon him) said -.
This incident happened exactly like this during the time of the Messenger (peace be upon him), but some people say: The Companions followed the Prophet (peace and blessings be upon him) in this extra rak'ah because the time was a time of new legislation; and therefore they said to him: "Did you add to the prayer?" He said: . Then the hadith completed as you heard. We say: The cause is not only this; because if the followers' following of the Prophet (peace and blessings be upon him) was for this cause - that is, with the possibility that he only added to the prayer - it would have been obligatory for the Prophet (peace and blessings be upon him) to hasten to clarify the ruling for those other than the Companions; because it is not permissible for the Prophet (peace and blessings be upon him) to delay clarifying the ruling from its appropriate time and occasion. And therefore we say that it is obligatory to follow the imam whatever his mistake or error may be; due to the generality of his saying (peace and blessings be upon him): to the end of the hadith.
Other than that?