This paper examines how discriminatory input pricing by the upstream monopolist affects the R&D choices of downstream duopolists in the presence of R&D spillovers. We show that the monopoly supplier can benefit from a precommitment to uniform pricing because under uniform pricing the downstream firms invest more in R&D, leading to larger output and thus benefiting the supplier. When R&D spillovers are sufficiently large, the downstream firms are also better off under uniform pricing. Moreover, social welfare is always higher under uniform pricing.