The sustainability transitions literature addresses globally pressing sustainability challenges. However, the scholars in the field trend towards using the term "sustainability" in a manner that is not reflexive, often just assuming that the studied cases contribute to more sustainable modes of production and consumption. In this paper, we suggest an alternative: a reflexive sustainability perspective that takes into account case selection issue, sources of unsustainability, double-edged sword dilemma, and boundary problem. Using this perspective as our starting point, we conduct a case survey, analyzing the extent to which such a perspective is considered in a number of selected case-based transition studies. We find that the deeper reasons for unsustainability and alternative sustainability solutions are often overlooked, sustainability trade-offs are mostly not considered, and the potential sustainability effects beyond the case boundaries are typically not reflected on. Based on these considerations, we provide scholars with some implications and suggestions on how to reflect on their own sustainability assumptions and contribute to more reflexive scholarship in the future.