Ohio Rev. Code § 4113.09
In all actions described in section 4113.03 of the Revised Code, any contract, rule, regulation, or device, the purpose or intent of which is to enable any employer to exempt himself from any liability created by sections 4113.03 to 4113.09, inclusive, and sections 2125.01 to 2125.04, inclusive, of the Revised Code, is to that extent void. In any action brought against any employer under sections 4113.03 to 4113.08, inclusive, and sections 2125.01 to 2125.04, inclusive, of the Revised Code, such employer may set off therein, any sum he has contributed or paid to any insurance, relief, benefit, or indemnity paid to the injured employee or the person entitled thereto on account of the injury or death for which said action was brought.
R.C. § 4113.09