Minn. Stat. § 219.81: CONTRARY CONTRACT DECLARED VOID.

Any contract, rule, or device whatever, the purpose or intent of which is to enable an employer to escape liability created by sections 219.77 to 219.83, is to that extent void. In an action brought against the employer under or by virtue of sections 219.77 to 219.83, the employer may set off any sum the employer has contributed or paid to any insurance, relief, benefit, or indemnity that may have been paid to the injured employee, or to the persons entitled to it on account of the injury or death for which the action was brought.