This study aims at exploring mathematics teachers' perceptions of the inclusion of computational thinking aspects into mathematics education and what challenges they may encounter when the notion is included in teaching mathematics. Eight mathematics teachers were interviewed; four teachers teach in Indonesian lower secondary schools (grades 7-9), and the remaining in upper secondary schools (grades 10-12). The interview focused on how teachers perceive the notion of computational thinking and its aspects (abstraction, algorithmic thinking, automation, debugging, decomposition, and generalization), their challenges in bringing the aspects into their teaching, and what support they need to integrate them into their classroom. Preliminary analysis of the data reveals that computational thinking is predominantly associated with problem-solving. Some aspects of computational thinking, such as generalization and decomposition, were already familiar within mathematics education, allowing teachers to comprehend the concepts easily. However, abstraction is an exception. Grasping abstraction is an obstacle for teachers since they preconceive the aspect associated with the abstract nature of mathematical objects. When discussing the challenges they may encounter, teachers are concerned about the competence of teachers in bringing the notion into mathematics teaching. A targeted development program for teachers is considered helpful for enhancing teachers' understanding of computational thinking and tackling the competence issue.