Developing robust web services is a difficult task. Field studies show that a large number of web services are deployed with robustness problems (i.e., presenting unexpected behaviors in the presence of invalid inputs). Although several techniques for the identification of robustness problems have been proposed in the past, there is no practical approach to automatically fix those problems. This paper proposes a mechanism that automatically fixes robustness problems in web services. The approach consists of using robustness testing to detect robustness issues and then mitigate those issues by applying inputs verification based on well-defined parameter domains, including domain dependencies between different parameters. This integrated and fully automated methodology has been used to improve three different implementations of the TPC-App web services and several services publicly available on the Internet. Results show that the proposed approach can be easily used to improve the robustness of web services code.