People are increasingly concerned about the trustworthiness of software that they use when acting within socio-technical systems. Ideally, software development projects have to address trustworthiness requirements from the very early stages of development using constructive methods to enable trustworthiness-by-design. We analyze the development methodologies with re-spect to their capabilities for supporting the development of trustworthy soft-ware. Our analysis reveals that well-established development methodologies do not specifically support the realization of trustworthy software. Based on find-ings, we propose a generic mechanism for extending development methodolo-gies by incorporating process chunks that represent best practices and explicitly address the systematical design of trustworthy software. We demonstrate the application of our approach by extending a design methodology to foster the development of trustworthy software for socio-technical systems.