Agent Doug Hendrickson confirmed the agreement Wednesday night.
The 34-year-old Mathis has been a steady part of Detroit's secondary since the Lions signed him two years ago. He had 42 tackles and nine assists last season, as well as an interception he returned 41 yards for a touchdown in an October loss to Buffalo.
Mathis spent the first 10 seasons of his career with the Jacksonville Jaguars before joining the Lions.
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