Do software engineering students need interdisciplinary skills? Do students learn different things from an interdisciplinary project work than from software development projects? How can a specific interdisciplinary project course be organized? This paper provides reflections about these questions, based on the experience gained through running a project-based interdisciplinary course thrice. This course is part of the master degree education at the NTNU, Trondheim, Norway. Students taking the course work in teams of five, often coming from study programs of quite different disciplines. There is no predefined project assignment, instead the teacher has only described an open-ended theme, within which different student teams then define their own project assignment. The paper provides some reflections and lessons learned that can be exploited for designing similar interdisciplinary team project courses in other universities.