Discussion of conceptual engineering within philosophy tends to focus on changes to concepts that result in changes in their extensions. Consider, e.g., changing the concept RAPE to include marital rape. This neglects a prominent view of concepts from psychology, namely Prototype Theory. Conceptual engineers should care about prototypes too. Even if marital rape is in the extension of RAPE, it is still a problem if the prototypical instance is, say, an attack by a stranger. Conceptual engineering targeting prototypes has a number of advantages, including avoiding some problems facing classic conceptual engineering, and opening up fruitful connections with machine learning.