The Lions acquired offensive lineman Rob Sims in a trade earlier this year with the Seahawks.
And the Lions have decided that they like the player who was working under a one-year tender to keep him.
Per a league source, Sims has signed a four-year extension. Terms are not yet available.
A five-year veteran, Sims started 14 games last year for the Seahawks. He has started all four games in 2010 with the Lions.