The addition of 'clinically significant impairment' (American Psychiatric Association, Diagnostic and statistical manual of mental disorders, Author, 2013) to the diagnostic criteria for autism in DSM-5 attempts to establish a threshold for the condition. However, the increased prominence of the neurodiversity paradigm and social model of disability runs counter to the idea that characteristics of autism are fundamentally impairing. Consequently, diagnostic criteria for autism are becoming misaligned with the contemporary views of 'disorder' and 'disability'. In this commentary, we outline six clinical issues that arise from this misalignment during diagnostic assessment for autism, and the tension this creates in making diagnostic decisions. We conclude by considering ways the 'clinically significant impairment' criterion could be changed, and the implications this would have on clinical practice, and the concept of autism.