We investigated whether low-functioning children with autism generalise labels from colour photographs based on sameness of shape, colour, or both. Children with autism and language-matched controls were taught novel words paired with photographs of unfamiliar objects, and then sorted pictures and objects into two buckets according to whether or not they were also referents of the newly-learned labels. Stimuli matched depicted referents on shape and/or colour. Children with autism extended labels to items that matched depicted objects on shape and colour, but also frequently generalised to items that matched on only shape or colour. Controls only generalised labels to items that matched the depicted referent’s shape. Thus, low-functioning children with autism may not understand that shape constrains symbolic word–picture–object relations.