This paper investigates the gambling preference of Chinese investors in the convertible bond (CB) market through a natural experiment—the 2018 amendment of Article 142 of the Company Law. Utilizing CB issuance data from 2016 to 2023, we employ a cohort difference-in-difference approach and find a 4% to 7% increase in IPO premiums for high-repurchase-expectation CBs across various measures. This significant increase indicates that the legal revision reshapes investors’ expectation and adjusts their valuation of CBs. Furthermore, the event-study analysis reveals the escalating impact of legal revision, driven by the herding behavior of gambling investors.