Isaac Assenso signed for the Celts in September 2022, having most recently been with Scarborough Athletic.
The right-back has been training with the club since pre-season, as he concluded his rehabilitation from an ACL injury.
The 25-year-old, who can also operate in defensive midfield, came through the ranks at Leeds United, before moving to Scunthorpe United in 2015.
After departing Scunthorpe in 2016, he would spend time with Ossett Town, Hartlepool United and Belper Town, before making the move to the Seadogs.