Demi Lovato Covers Lil Wayne in Concert

Demi Lovato is expanding her repertoire ... to Lil Wayne songs!

The young pop star hit the stage this weekend at Hammerstein Ballroom in NYC, where she performed a stripped-down version of Weezy's song "How To Love."

Demi sounded pretty good, but committed the ultimate cover sin: She forgot the lyrics to the song!

Check out her flub above -- and watch the full performance over on YouTube.

Khloe Kardashian Weight Loss
See Her New Curvy Figure! -- Style Blazer

• ‣  Amanda Bynes reacts to alleged marijuana pics - Amy Grindhouse
• ‣  Actress actually has time for 2-hour workouts - Celebuzz
• ‣  Kendall Jenner SLAMMED on Twitter - Gossip Girl
• ‣  Real Housewife locked out of her house! - Celeb Dirty Laundry