Once teaching-learning events are conceptualized as inter-discursive encounters, it becomes clear that mathematics classroom talk is rife with invisible pitfalls. There are many types of unacknowledged discursive gaps, some of them necessary for learning and some potentially harmful. Such gaps may exist also between the teacher's intentions and her habitual moves, most of which are too brief and automatic to be controlled. Unbeknown to the teacher, her basic communicational routines may deprive her students of proper learning opportunities. Some seemingly innocent teaching routines may also constitute invisible crevices through which prejudice and injustice enter the conversation on mathematical objects. In this talk, I argue that if the devil is in the finest detail of classroom communication, it is the detail that must be considered in the attempts to exorcise the devil. I begin with illustrations of these claims and conclude with a reflection on what teachers can do to sensitize themselves to discursive pitfalls and to eradicate or change those routines that carry the greatest risks.