While language aptitude has been investigated actively within second language research, there is a current dearth of research on the effects of aptitude in cases of attrition. The aim of the present investigation was to explore the role of language aptitude for L1 proficiency in speakers who experienced a break with their L1 setting prior to puberty. Twenty-five L1 Spanish-L2 Swedish bilinguals residing in Sweden participated in the study, and 15 native speakers of Spanish living in Chile were recruited as controls. The L1 proficiency was measured by means of a grammaticality judgement test (GJT) and language aptitude data were obtained through the "Swansea Language Aptitude Test" (Meara et al. 2003). Results showed a positive correlation between GJT performance and language aptitude. More specifically, the bilinguals with above-average aptitude were more likely to score within the native range on the GJT than those with below-average aptitude. It was also seen that among the participants with below-average aptitude, GJT scores were related to daily L1 use. In view of these findings, we suggest that language aptitude has a compensatory function in language attrition, helping the attriter to retain a high level of L1 proficiency despite reduced L1 contact.