Katy Perry has been working on her new album with ''soulmate'' Bonnie McKee.

The 'Fireworks' hitmaker has been getting help writing songs for the follow-up to her massive album 'Teenage Dream' with Bonnie, who she has previously collaborated with on singles 'California Gurls', 'Teenage Dream', 'Last Friday Night (T.G.I.F.)' and 'Part of Me'.

Bonnie told MTV news: ''We were just in [Katy's hometown of] Santa Barbara and we wrote three or four songs, I guess. So I have four songs with her coming out.''

Singer-songwriter Bonnie puts her great working relationship with katy down to their similarity. On one occasion the pair coincidentally both penned tracks called 'The One That Got Away', and while Katy's was on 'Teenage Dream' Bonnie's version was recorded by Miranda Cosgrove.

Bonnie added: ''Katy and I are really similar. That's kind of how we became friends. We met at Wasteland on Melrose [Avenue in Los Angeles], a thrift store. We just are totally on the same level ... We're just soulmates in that way, I guess.''

Katy's music has grown since her last album and she is taking a ''new approach.''

Bonnie added: ''I'm really excited for the world to hear it because she's taking a new approach. And I don't want to say too much about it, but it's definitely different. It's definitely a little more mature than the 'California Gurls' of yesterday.''

Katy also appears in Bonnie's first-ever music video, for 'American Girl', off her upcoming debut album.