When a defendant argues for the first time on appeal that his guilty plea was not knowing and voluntary because he was not informed of the elements of the offense, and it is undisputed that he did not in fact know the elements of the offense at the time of his plea, must he additionally make a case specific demonstration of prejudice in order to prevail?

When a defendant argues for the first time on appeal that his guilty plea was not knowing and voluntary because he was not informed of the elements of the offense, and it is undisputed that he did not in fact know the elements of the offense at the time of his plea, must he additionally make a case-specific demonstration of prejudice in order to prevail?