The Lions already re-signed their starting defensive tackles from 2015, but they found more help at the position on Thursday.
Former Bills defensive tackle Stefan Charles is signing a one-year deal with the Lions. NFL Network was the first to report the move.
Charles, 27, was a restricted free agent, but Buffalo declined to tender him. In 13 games last season, he had 13 tackles, one sack and one forced fumble.
An Ontario native who played collegiately at University of Regina in Saskatchewan, Charles signed with the Titans as an undrafted rookie in 2013. After Tennessee cut him that August, the Bills added him to their practice squad and put him on the active roster that October.
Charles played eight games as a rookie with 12 tackles, one sack and one forced fumble, and he had his best year in 2014, finishing with 23 tackles and three sacks in 16 games.