No officer, department head, employee, or board or commission member shall make or participate in the making of any contract with the city in which he may be in any manner financially interested, directly or indirectly. Any such person who has such an interest in any proposed contract shall make known that interest. The willful concealment of such a financial interest or the willful violation of this section shall constitute malfeasance in office or position, and any violator shall forfeit his office or position. Violation of this section with the knowledge express or implied of the person, firm, or corporation contracting with the city shall render the contract void.