While firms frequently rely on patents as an appropriability mechanism, they face a tension between preserving their ability to invent cumulatively and deterring imitation of commercialized products. We examine this tension in the context of Virtual Patent Marking (VPM). Exploiting information on the timing of marking, we show that marking increases rivals’ follow-on inventions to marked patents. Assessing implications for firms’ cumulative inventions, we find no evidence that such spillovers are associated with greater preemption of firms’ future inventions; instead, they create opportunities firms subsequently build upon. Implications for the appropriability and vicarious learning literatures are discussed.