Katy Perry has her friends as well as ex-husband Russell Brand worried ever since she started dating John Mayer.
The 27-year-old singer went to a late-night house party with new man, singer John Mayer, 34, recently.
John has previously dated Jennifer Aniston, 43, Cameron Diaz, 39, Jennifer Love Hewitt, 32, Kim Kardashian, 31, and Taylor Swift, 22, amongst others.
“John has a big reputation as a serial womaniser. If people thought her ex, Russell Brand, was bad, John is notoriously a lot worse,” Contactmusic quoted an insider as telling the Daily Star.
“Katy''s friends are worried this is just a rebound bit of fun but will end with her getting really hurt,” the insider added.