Open phenomena including open resources, processes such as crowdsourcing and their effects have initiated fundamental shifts in the way organizations conduct their business. With increasing recognition of the value of openness, represented by principles such as transparency, access, participation and democracy, crowdsourcing has established itself as a suitable mechanism for various use-cases ranging from decision-making to idea generation, microtasking and problem-solving. Increasingly, organizations have begun to crowdsource to their employees instead of external crowds. However, few studies analyze concrete use-cases of internal crowdsourcing and further research is needed. We propose that internal crowdsourcing is particularly useful for software requirements engineering (RE) within organizations. Crowd-based RE alleviates shortcomings of traditional RE approaches such as requiring co-presence or lacking representativeness. Research on crowd-based RE remains scarce, particularly concerning intra-organizational settings and the post-implementation phase of software projects. Defining high-quality requirements demands contextual expertise as well as experience and internal crowds seem to be decidedly well-suited for solving RE-related tasks as they exhibit these exact traits. Following a design science research approach, we develop design principles for internal crowd-based RE and instantiate them in a public-sector organization leading to a holistic evaluation. Subsequently, we formulate recommendations for establishing crowd-based RE in intra-organizational settings.