In a corpus of student/tutor dialogues on mathematical proofs, tutors use their evaluations of the correctness of proof steps in order to generate pedagogically suitable feedback. This motivates the need for support from a reasoning module for verification of proof steps in mathematics tutorial dialogue systems. In such a system the support from the mathematical domain reasoner is combined with the benefits of natural language interaction with a simulated tutor. In this talk I will present two important steps towards realising such a system. First, I present a domain-independent method for automatically verifying correct proof steps and detecting standard reasoning errors which utilises general-purpose mathematical knowledge. Second, I show how a dialogue manager can interface with the domain reasoner. The dialogue manager can thus provide a single representation of information, like the linguistic and mathematical interpretation of the previous proof step, which is needed to instantiate tutor actions such as hints.