Katy Perry is still having a tough time dating infamous ladies' man John Mayer, so the "Firework" singer has turned to an unlikely source for advice - Jennifer Aniston.

Mayer and Aniston dated for about a year before Aniston got engaged to writer and actor Justin Theroux, and friends of Perry said the singer has sought out Aniston for tips on how to control Mayer's playboy ways.

"Jennifer gave Katy her number and told her to call any time, but she didn't expect her to take the offer so seriously," a source said. "Now Katy's in contact and asking her for tactics on how to tame him, but John seems to know about it and isn't happy that his ex has become so involved in his relationship. Jennifer's trying to wean Katy off, telling her that she doesn't want John to think she's meddling, but Katy won't be put off."

Perhaps Perry started making the calls after she heard that Aniston felt she should dump Mayer and move on. An insider close to the former "Friends" star said several weeks ago that Aniston was telling pals she wished Perry would learn from the mistakes in the relationship between Aniston and Mayer, according to a report from Perez Hilton.

"Katy should really watch out. Take it from Jen. She's been there and done that," the source said. "And it took her years to recover. Jennifer gave John more than a year to prove himself as marriage material. Katy needs to be warned about John's hypnotic ways before its too late."

But Perry is only looking to "tame" Mayer, not dump him. In fact, friends said she is completely head over heels for the singer and guitarist.

"Katy is besotted with John," an insider said. "When they first started dating, she swore she wouldn't fall for his womanizing ways, but now she can't get enough of him and has been telling friends that he's not the player that people believe he is. But her friends aren't convinced and are worried that she's just falling for another bad boy."

Tags: Katy Perry John Mayer Jennifer Aniston