Bunn has not had that many chances to oust Rovers number one Paul Robinson from his place but has impressed when he has been given the chance to.
He told the Lancashire Telegraph: "I'm absolutely delighted to get another two and a half years at the club.
"It couldn't have gone any better. I've played a few games recently, which I thought I did well in, and I want to take it further.
"To get a new deal is great news."