Requirements Engineering in safety-critical systems must systematically develop and evaluate requirements for functional safety and cyber security in parallel. Currently this is done in a piecemeal, because the industry standards for safety and security are still placed highly isolated from each other. This previously established separation of the two "disciplines" each with its own standards and procedures is not sustainable because of dependencies and mutual influences are overlooked. In addition, a separate procedure is inefficient because many functions have to be touched several times. An integrated approach for the development and verification of requirements is essential in order to make these two quality requirements manageable. Our presentation shows with practical industry experience of Vector and Hella how the dependencies and interactions between safety and security requirements in Requirements Engineering methodically and systematically be considered. First, we describe a practical approach to the safety requirements. On this basis we integrate development for security requirements. The advantages of an integrated safety and security requirements engineering methodology are illustrated tool based on a specific example.