In this study, we examine instances of peer involvement in L2 classroom interaction when student initiatives receive an observably insufficient teacher response. The data for this study consists of videorecordings of an EFL classroom in higher education. Using Conversation Analysis (CA), this study shows that peers get involved in and extend student-initiated sequences (1) to provide a response to student initiatives that receive the teacher's display of lack of knowledge and (2) to offer support in challenging a teacher response to student initiatives. In this way, peers contribute to resolving emergent knowledgerelated troubles in teacher responses. Such peer involvement is found to create learning opportunities not only for the students but also for the teacher by changing the epistemic asymmetry and participation framework in the classroom. The analysis reflects the dynamics of classroom interaction and provides implications for our understanding of peer roles in whole-class interactions. (c) 2022 Elsevier Inc. All rights reserved.