Jamie became David Artell’s third addition ahead of the 2025-26 season on a two-year deal.
The 33-year-old attacking midfielder made the move to Blundell Park following a three-year spell with Bradford City where he made 125 appearances and racked up 32 goal contributions.
Walker made his move to the Bantams permanent ahead of the 2022-23 campaign and most notably helped the West Yorkshire club achieve League One status in dramatic fashion at the end of the 2025-26 campaign.
The Scottish forward graduated from the Heart of Midlothian Academy, where he signed his first professional contract, before going on to make 240 first team appearances across two spells, scoring 54 goals and helping them to the Scottish Championship title on two occasions.
In between his two spells in Scotland, Walker joined Wigan Athletic in January 2018, before signing for Peterborough on loan for the first half of 2019-20.
Walker also made 18 appearances as a Scottish youth international across multiple age groups.