In this study both adolescents with autism spectrum disorder (ASD) and typically developing controls were presented with conditional reasoning problems using familiar content. In this task both valid and fallacious conditional inferences that would otherwise be drawn can be suppressed if counterexample cases are brought to mind. Such suppression occurs when additional premises are presented, whose effect is to suggest such counterexample cases. In this study we predicted and observed that this suppression effect was substantially and significantly weaker for autistic participants. We take this as evidence that autistics are less contextualised in their reasoning, a finding that can be linked to research on autism on a variety of other cognitive tasks.