Jennifer Aniston's musician beau John Mayer is going to propose to her on her 40th birthday

Jennifer Aniston's musician beau John Mayer has custom-made an engagement ring designed for her birthday on Feb 11, 2009, reports mirror.co.uk.

Mayer said "I think I'd be pretty good at proposing. I'd figure that out. I'd get creative,"

The couple, both of them, have dated on and off since April 2008.

Jennifer Aniston had been married to Hollywood superstar Brad Pitt for 4 years before their split in 2005.