In universities worldwide, there has been a movement away from mono-disciplinary towards multi-, inter- and transdisciplinary education, motivated by the notion that complex societal issues call for more than a single disciplinary perspective. To prepare students for a role in addressing these issues, flexibility within educational programs is needed for students to move within, across and beyond disciplines. Contrary to the intended orientation on societal issues, multi-, inter- and transdisciplinary education appear in the current discourse regularly as aims in themselves, as if they were distinctive types of education that one should adopt at the level of a course or a program. We argue that education could more flexibly utilize and create free space: continuously questioning, also together with students, what sorts of perspectives and disciplinarities problems require. Therefore, we propose "boundary crossing" as an alternative way of thinking about multi-, inter- and transdisciplinary education. At many universities, organizing for flexibility already gains some traction. However, we believe that a shift of focus towards more open ways of transgressing disciplines in the field of higher education is vital for furthering the transformative potential of multi-, inter- and transdisciplinarity for students to being and becoming the professionals that society needs.