This article discusses the findings of a case study that explored the use of explanatory talk in mathematics teacher education lessons on how to teach the concept of place value. The Mathematics Discourse in Instruction framework guided the study, in particular the element of naming in explanatory talk. Three teacher educators' lessons on the teaching of place value of whole numbers were observed and video recorded. Findings indicate that across all the lessons, 66% of the naming was mathematical and was seen to provide opportunities for student teachers to learn to use mathematical terms correctly, while 34% of the naming was non-mathematical and might have constrained student teachers' understanding of some concepts related to place value. Furthermore, two-thirds of the non-mathematical naming was use of ambiguous pronouns, which could have been avoided. The findings suggest that teacher educators need to pay more attention to correct mathematical naming of terms related to place value. How mathematical concepts are named in teacher education is important because correct naming is likely to help student teachers learn to regard mathematical talk as an important part of their work of teaching.