The 20-year-old Scouser made his first-team debut in February when he started the FA Cup fourth-round replay win over Shrewsbury Town at Anfield.
That was due reward for several hard months of rehabilitation as he battled back from a knee injury sustained with the U23s last September.
Lewis was a member of the first team’s USA pre-season tour party last summer and played against the likes of Borussia Dortmund and Sevilla.
A former winger and midfielder, Lewis has settled into a left-back role over the last few seasons. His delivery from out wide has been a notable asset while his left foot has become a valuable weapon at set-pieces.