When a bilingual speaker has a larger linguistic sub-system in their L1 than their L2, how are L1 categories mapped to the smaller set of L2 categories? This article investigates this ‘subset scenario’ (Escudero 2005) through an analysis of laterals in highly proficient bilinguals (Scottish Gaelic L1, English L2). Gaelic has three lateral phonemes and English has one. We examine acoustics and articulation (using ultrasound tongue imaging) of lateral production in speakers’ two languages. Our results suggest that speakers do not copy a relevant Gaelic lateral into their English, instead maintaining language-specific strategies, with speakers also producing English laterals with positional allophony. These results show that speakers develop a separate production strategy for their L2. Our results advance models such as the L2LP which has mainly considered perception data, and also contribute articulatory data to this area of study.