Pop-singer Cyndi Lauper sang the National Anthem at this weekend's U.S. Open tennis event and screwed up a line from the song during a tribute to the 9/11 victims.

In the middle of the song, Lauper sang, O'er the ramparts, we watched as our flag was still streaming. The line is: O'er the ramparts we watch'd were so gallantly streaming.

It was a relatively minor flub, but Lauper felt the need to explain herself after the event.

Whew, I just did the anthem for the US open. It was an awesome experience. I got choked up in the middle remembering 9/11, Lauper wrote on Twitter.

Lauper isn't the only person to screw those particular lines. While singing the anthem during the Super Bowl, Christina Aguilera messed up the same exact line. Except, Aguilera's screw up was arguably a lot worse.

She sang, What so proudly we watched at the twilight's last gleaming?

Perhaps, someone should make some cue cards for these pop stars.