There are two approaches to safety - regulated and managed - which reflect the debate on how to best handle uncertainty. On the one hand, regulated safety involves technical and procedurals barriers against predictable events and thus focuses on diminishing uncertainty. On the other hand, managed safety focuses on the development of organizational capacity to proactively cope with unexpected events. Research shows that the extensive development of regulated safety rules may jeopardize managed safety. Paradoxically, research also shows that only their mutual reinforcement can guarantee safety in complex environments. Through a qualitative case study of the implementation of reliability seeking practices in one of the European power plants, this paper focuses on the development and the implementation of safety rules. Our results show that despite the explicit intention to develop human safety competence, the reliability seeking practices reinforce regulated safety, which diminishes rather that copes with uncertainty. This paper revisits the notion of managed safety and its articulation with regulated safety requirements.