This article analyses a practice of formative peer-assessment based on an experience in university teaching innovation. From a review of the literature on feedback for self-regulation, the traits of formative assessment practices are determined and a task and the assessment criteria are designed in a consistent way with these traits. After the application of the experience, the results are discussed in terms of students' involvement; activity performance of said experience and of the whole subject; motivation and self-perception of learning and of the competency-based development of the students. The results show positive effects on the involvement, motivation and learning perception but not on performance improvement, suggesting that future research should address the effects of self-regulating feedback on the estimated learning from objective measurements and should expand the studies of the effects of these practices on the immediate and future self-regulating capacity.