We study the effect of hiring temporary workers on the voluntary turnover of permanent employees within the context of a dual labor market. Using a unique longitudinal dataset with individual-level monthly payroll data for an average of 60,000 individuals belonging to 278 organizations in Spain during an eight-year period, we find a positive association between temporary worker inflows and the voluntary turnover of permanent workers. We also find that recent permanent worker downsizing reduces this positive association. Thus, the costs of disruption and identity threat associated with temporary hiring seem to outweigh the potential benefits of helping hands for permanent workers. These findings suggest that the shift toward employment flexibility may have affected the mindset of permanent employees: hiring temporary workers may be changing the social contract even in a regulatory environment characterized by strong protection for permanent workers.