Making in schools, where students produce and share physical or virtual objects, has garnered increased global attention for its potential to foster twenty-first century learning in STEM and develop students' inventiveness, creativity, and entrepreneurial thinking. However, there has been limited attention paid to how maker-centred learning environments might plan a role in how "undergraduate university students" access, belong to, and persist in STEM-related pathways and majors. A regression analysis revealed that sophomores enrolled in the studied "maker" course were 44% more likely major than a matched comparison group (who did not take the course) to maintain or declare being a STEM. Through an identities-in-practice theoretical lens, we also analyzed qualitative interviews with 10 of the sophomores enrolled. The sophomores interviewed developed skills, expressed varying feelings of community and belonging, and evolved in their conception of Making in relation to STEM during the course. Their identities were also confronted and shaped during the course -- either reinforcing or competing with their identity as a STEM person. These findings support prior calls in the literature to go beyond making as just a way to instil twenty-first century skills and consider how maker courses could more intentionally foster all students' STEM identity.