Mich. Comp. Laws § 419.54

Sec. 4. No contract of employment, insurance, relief benefit, or indemnity for injury or death entered into by or on behalf of any employe, nor the acceptance of any such insurance, relief benefit or indemnity by the person entitled thereto, shall constitute any bar or defense to any action brought to recover damages for personal injuries to, or death of such employe: Provided, however, That upon the trial of such action, the defendant may set off therein any sum it has contributed toward any such insurance, relief benefit or indemnity that may have been paid to the injured employe, or, in case of his death, to his personal representative.