We investigate how an inquiry-oriented, dynamic, open-source calculus textbook shaped one college instructor's planning. We rely on Dietiker et al.'s [(2018). Research commentary: Curricular noticing: A framework to describe teachers' interactions with curriculum materials. "Journal for Research in Mathematics Education," 49(5), 521-532. https://doi-org.bibliotheek.ehb.be/10.5951/jresematheduc.49.5.0521] curriculum noticing framework to situate the instructor's actions during lesson planning using data from surveys, logs and interviews. The instructor's planning practices are characterized by intense use of the textbook, including creating additional curricular material related to its content. Our observations suggest that the textbook supported and influenced the instructor in implementing his inquiry-oriented visions and goals while planning his lessons. We conclude by suggesting further investigation of how textbooks shape undergraduate mathematics education and the textbooks' role in shaping undergraduate mathematics planning practices.