Security concerns are increasingly guiding both the design and processes of software-intensive product development. In certain environments, the development of the product requires special security arrangements for development processes, product release, maintenance and hosting, and specific security-oriented processes and governance. Integrating the security engineering processes into agile development methods can have the effect of mitigating the agile methods' intended benefits. This article describes a case of a large ICT service provider building a secure identity management system for a sizable government agency. The project was a subject to strict security regulations due to the end product's critical role. The project was a multi-team, multi-site, standard-regulated security engineering and development work executed following the Scrum framework. The study reports the difficulties in combining security engineering with agile development, provides propositions to enhance Scrum for security engineering activities. Also, an evaluation of the effects of the security work on project cost presented.