More research into the disciplinary content and context of doctoral education is needed. The aim of this study is to address this gap by investigating norms in supervision in the specific context of life science. Our approach focuses on the humour in two supervision meetings, looking at who and what is positioned as funny in longer instances of humour. Using an analytical framework inspired by positioning theory, we found that both conceptual knowledge and personal identity were positioned through jokes during supervision meetings. The humour dealt with disciplinary norms on several levels, from ‘Which numbers are aesthetic?’ (Answer: even numbers) to ‘How best to communicate with team members in another country?’ We noticed both positive and negative positionings within the jokes. Humour has several functions: one is to create a relaxed atmosphere; another is to offer criticism in a kind way. Since supervision is also characterised by power distances, it is important that supervisors be aware of the ambiguity of humour.