However his first season in the Championship wasn't as much of a success which resulted in relegation back down to the third tier. Peterborough started off strongly and Lewis was first choice keeper nearly all the season, however after fracturing his kneecap (and playing a whole half with it fractured) against MK Dons in the play-off semi final, he was forced to miss the second leg and final through injury. Peterborough went on to win promotion, defeating Huddersfield 3–0 in style in the final. During his fifth season at Peterborough, Lewis was replaced as first choice keeper permanently by Paul Jones and only made 12 appearances. His last appearance for the club came on 14 February, in a 3–1 loss at Cardiff City. On 30 April, Lewis was released by the club at the end of his contract, with Cardiff City and Ipswich Town interested in signing him.