An important premise for the interpretation of the results in time perception studies employing virtual reality (VR) techniques is that the method itself does not affect time perception. I will present a study in which we tested this assumption by comparing timing performance in a real-life and a VR scenario. Our participants performed two timing tasks, requiring the production of an interval defined either by numerical values or by the duration of a physical process. The results show that the experience of immersive VR exclusively alters judgments about the duration of physical processes, whereas judgments about the duration of abstract time units are unaffected. These results demonstrate that effects of VR on timing performance are not driven by changes in time perception itself, but rather by altered expectations regarding the duration of physical processes. I will discuss the implications of this finding for the interpretation of VR studies in time perception research.