All contracts executed by any incorporated town or any officer thereof which involve the construction or doing of any work involving the employment of labor shall contain a provision that the contractor shall accept, insofar as the work covered by any such contract is concerned, the provisions of the Workmen's Compensation Act of 1915¹ and the supplements and amendments thereto, and that the said contractor will insure his liability thereunder or file with the incorporated town with whom the contract is made a certificate of exemption from insurance from the Bureau of Workmen's Compensation of the Department of Labor and Industry.

Every officer of any incorporated town who shall sign on behalf of the incorporated town any contract requiring in its performance the employment of labor shall require, before the said contract shall be signed, proof that the said contractor with whom the contract is made shall have accepted the Workmen's Compensation Act of 1915 and any supplements or amendments thereto, and proof that the said contractor has insured his liability thereunder in accordance with the terms of said act or that the said contractor has had issued to him a certificate of exemption from insurance from the Bureau of Workmen's Compensation of the Department of Labor and Industry.

Any contract executed in violation of this section shall be null and void.