Students' choice of college major is related to their interests (Porter and Umbach in Res High Educ 47:429-449, 2006), and students whose major is well-aligned with their interests are more likely to persist in that major (Allen and Robbins in Res Higher Educ 49(1):62-79, 2008) and complete a college degree in a timely manner (Allen and Robbins in J Couns Psychol 51(1):23-35, 2010). This study investigates whether a specific signal (i.e., Low, Medium, or High fit) that high school students receive about the alignment between their initial choice of planned major and their measured interests has an impact on the subsequent certainty of their initial choice of planned major. A regression discontinuity design was used to investigate the stability/increase in planned major certainty across two ACT administrations for students with Medium versus Low fit and High versus Medium fit. Results did not provide evidence that the signal is effective; possible explanations and recommended future research are discussed.