She was supposed to sing the line "O'er the ramparts we watched, were so gallantly streaming?" but instead ended up repeating an earlier line, with a slight variation.
She sang, "What so proudly we watched at the twilight's last gleaming", which is the same line from earlier in the song but with the word 'watched' instead of the word 'hailed', reports News.com.au.
The error caught the attention of people immediately and set social networks abuzz with many users commenting on the error.
Aguilera's representative did not immediately return a call and email seeking comment.(ANI)