The transformative turn in research and innovation (R&I) policy calls for new approaches to monitoring and evaluation, yet most evaluands are still rooted in previous policy paradigms. For evaluators tasked with conducting ex-post evaluations, this situation creates multiple challenges that have received little attention to date. In this 'voice from the field', I argue that times of paradigmatic change require an increased awareness about discursive politics, heightened expectations, uncertainties, and the differences between the old and the new in evaluations. Based on recent experiences from an ex-post evaluation of the R&I programme "City of Tomorrow," I provide some suggestions for coping with these challenges.