An assignment of future wages payable under the provisions of section 342 of this title shall not be valid, if made to the employer from whom such wages are to become due, or to anyone in behalf of such employer, or if made or procured to be made to anyone for the purpose of relieving such employer from the obligation to pay under the provisions of section 342. Such employer shall not require an agreement from an employee to accept wages at any other period as a condition of employment.