The purpose of this article is to clarify the concept of good faith in the context of constitutional interpretation. The need for good faith in constitutional interpretation stems not only from the specific political context of the crisis of liberal constitutionalism, but also from the very nature of constitution as a legal document, and above all from the irreducible sphere of discretion in constitutional interpretation. In my opinion, the concept of constitutional good faith should be understood as an instrument for limiting the discretionary power of interpreters and enhancing the legitimacy of the interpretative decisions they take. However, for the requirement of good faith to become an operative standard of constitutional culture it needs normative justification. In my view, such a credible justification for the concept of good faith in constitutional interpretation is provided by the philosophy of reflexivity. A reflexive account of good faith can be an instrument for limiting discretion in the process of constitutional interpretation, while at the same time contributing to deepening the social legitimacy of constitutional practice. In this way, such an approach can make constitutional practice more resilient to abuse.