This article contributes to the debate on how an international crisis may contribute to ontological security. We argue that ontological security can paradoxically be achieved through escalating practices capable of provoking international crises. By merging ‘practices’, a fairly distinct theoretical perspective of International Relations, with ontological security, we seek to expand Jennifer Mitzen’s premise that “even dangerous routines provide ontological security” and consider practices as a source of attaining ontological security. To partake in the practical turn in ontological security studies, we borrow the concepts of Practice Turn in IR, habitus (disposition), and field (environment). After substantiating the connection between the two theories, we take the demise of the INF Treaty as an example of a crisis. We argue that the INF Treaty, as a field, has become a source of ontological threat to both the U.S. and Russia. Following the end of the Cold War, the U.S. and Russia have constantly changed their habitus by developing key missile technologies and deteriorating bilateral relations. Accordingly, the changed habitus no longer conformed to the realities of the field, making its delegitimization by both sides self-evident.