Justin fan Jessica Biel

Jessica Biel was mortified when boyfriend Justin Timberlake caught her listening to his music.

The 'Easy Virtue' actress usually takes careful measures to ensure the 'SexyBack' singer doesn't catch her listening to his albums, but was found out during a surprise phone call.

She revealed: "I have to really watch out because I sing Justin's songs at home.

"When we first started hanging out I had to be really careful because he used to call me and I'd be blasting - and I mean blasting - his music while I was in the pool, swimming with my dogs. He'd call me and I'd have to fly out of the pool, drop the volume and be like, 'Hey, what's going on? I'm just at the pool, chilling out.'

"And he caught me once actually, we were on the phone and he goes, 'Are you playing 'Justified'?' I was like, 'No! I'm not!' "