This article sheds light on the linguistic and extralinguistic conditions that determine the likelihood of L1 grammatical attrition in late sequential bilinguals. We explore whether aspectual interpretations associated with the present tense may be a vulnerable area for the native grammar of 30 late Spanish-English bilinguals who have settled in the UK for over 15 years. Attrition of this property in L1 Spanish grammars has been reported by Cuza (2010. On the L1 attrition of the Spanish present tense. Hispania 93, no. 2: 256-272. doi:10.1353/hpn.2010.a382874) for Spanish-English bilinguals in the USA and Canada. Our finding of no attrition for UK-based Spanish bilinguals suggests that in Cuza's study, attrition may be mediated by dialectal variation in the L1 in the North American context, where Spanish is a widespread and visible community language. Further, we ascribe the absence of attrition to a specific characteristic of the grammatical distinction between the L1 and L2: where the L2 grammar provides options representing only a subset of the options available to the L1 for the corresponding grammatical property, attrition may be disfavoured.