This paper examines how the option of a regulated linear input price affects vertical contracting, where a monopolistic upstream supplier sequentially offers supply contracts to two symmetric downstream firms. We find that equilibrium contracts vary with production cost and regulated price level: If the regulated price is not too high, the option allows for price discrimination, but prevents foreclosure in the intermediary market. Indeed, if both cost and optional price are rather low, non-discriminatory input prices below cost may arise. Optional input prices are socially more desirable than a flat ban on price discrimination, as consumers benefit from more intense downstream competition.