English medium instruction (EMI) is widespread in European universities. In most such contexts, students and teachers are able to communicate in at least one other language, generally the shared L1. Recent studies in English-speaking countries and postcolonial settings have suggested that attitudes towards L1 use in EMI are changing, and that multilingualism in the classroom is accepted or even positively embraced. However, some studies in expanding circle countries such as Spain and Turkey indicate that this trend is not universal. This paper uses evidence from narrative frames administered to 60 EMI lecturers at 5 universities in northern Spain to investigate their attitudes to L1 use, identify how these intersect with their age, years of experience in EMI, gender and subject area, and shed light on their conceptualisations of EMI and emergent practices. Around half believed that L1 use was not acceptable, while most of the others only allowed the L1 in highly circumscribed conditions (to repair breakdowns in communication, to foster empathy outside the classroom, or to refer to local phenomena). Our evidence reflects the struggle to further the use of English in EMI settings where this language is a relative newcomer.