Categorisation is arguably the most important organising principle in semantic memory. However, elements that are not in a categorical relation can be dynamically grouped together when the context provides a common theme for these elements. In the field of sentence (and discourse) comprehension, alternatives to a focused element can be thought of as a set of elements determined by a theme given in the utterance context. According to Alternative Semantics (Rooth, 1985, 1992), the main function of linguistic focus is to introduce a set of alternatives to the focused element within an utterance. Here, we will investigate the contribution of the utterance context to the composition of focus alternative sets. Specifically, we test whether a focus alternative set can contain elements that belong to different taxonomic categories (i.e., that are not closely semantically related). Using a behavioural probe recognition experiment, we show that participants activate elements from another taxonomic category than the focused element as part of sentence comprehension. This finding suggests that the composition of a focus alternative set is not simply based on semantic relations between the members of the set and the focused element, but that contextual relations also play a crucial role.