 His stay at Charlton was extended on 15 April until the end of the season.Charlton acted swiftly in the following transfer window to bring Sullivan to the club on permanent basis after a string of impressive performances, securing a two-year deal on 31 May 2011.Sullivan made his first appearance for Charlton after signing permanently in the summer when he came on as a sixth-minute substitute against Leyton Orient after Ben Hamer was sent off for handling the ball outside his area.