The Northern Ireland international, who has spent two seasons with the Pirates, is regarded as one of the best right-backs in the lower leagues.
"I've been really pleased with Michael's attitude and approach to the game since I've worked with him," boss John Ward told the club's official website.
"He wants to try to improve as a player with Bristol Rovers, which is good news for everyone. He has been an absolute diamond in terms of our back five and has played a very big part in us getting ourselves into a safe position."
Bristol Rovers sit 12th in the League Two table.