John Mayer has admitted to having some doubts about collaborating with his girlfriend Katy Perry in case it had a negative effect on their relationship.

The pair worked on a single entitled Who You Love for Mayer's Paradise Valley album and while they are both really happy with how it turned out, he had some initial doubts about recruiting her for the song.

Speaking to z100 radio station he explained, "I had this idea that just sat around for a while and I thought, 'Maybe I'll finish it someday', and I played it for Don Was who was producing the record with me and he said, 'Get Katy to sing on it'.

"Now, he could say that because he doesn't have to worry about all the hang ups that I'd have to worry about. She was an artist in the studio and a partner out of the studio. It was really professional. There was a moment where she was like, 'Let me just go through it once', and the way I work is, 'Let's get this and that and that' and she was like, 'Let me try it my way'."

He added that they tend to keep their relationship separate from their careers, apart from their collaborations, "We were just fine before we met each other, that's what we say – 'You were find before I met you, you don't need my advice' and vice versa."