This paper explores the way design rules are developed and enacted. Literature on design stresses that scientific knowledge should be used as input for constructing a coherent reper-toire of design rules. In line with the reflective cycle, these rules have to be tested and refined during their application in organizational praxis. However, in this paper we argue that do not particularly consider this process as linear and unproblematic. More specifically, our research reveals major impediments to the establishment of allegedly tested and grounded design rules. The paper illustrates this by drawing on a longitudinal case study on the evolution of a piece of design knowledge. As a result, the study provides an understanding of the specific co...