Employing student-driven project work in a higher education setting challenges not only the way in which we understand students' learning and how we define the expected learning outcomes, it also challenges our ways of assessing students' learning. This paper will address this question specifically and illustrate with a case that highlights some of the challenges that may arise in practice when assessing student-driven, problem-based projects. The case involved an assessment situation in which a discrepancy arose between the internal and external examiner in relation to what was valued. The discrepancy had consequences not only for the concrete assessment of students' work, but also for the validity of the problem-based university pedagogy in general, and it raised the question of how to assess students' work adequately. The research focus of this study was to explore the implications of assessing student-driven projects within a progressive approach to higher education teaching, along with the potential underlying issues. We found a need for clear assessment criteria while insisting on a space for students' creativity and reflexivity as essential parts of a learning process. The paper thus makes a case for the notion of reflexivity as an assessment criterion to be integrated into learning objectives.