This term he has made just one start, in the Carling Cup defeat at Southend, after falling down the pecking order following the arrival of David James.
"Dean's a quality goalkeeper and is just the kind of player I want on our books," boss Keith Millen told the club's official website.
"He's been very professional in his approach this season and continues to work terrifically hard in training.
"He wants to play like every other player but he doesn't moan or cause any trouble, he just gets his head down and gives 100%," Millen added.
Source: BBC Sport
Source: BBC Sport