Ever since its introduction by Christian Lehmann in 1982, the term ‘degrammaticalization’ has been the subject of much controversy. There has been considerable disagreement about what kind of phenomena the term refers to, and indeed if degrammaticalization exists at all. In this paper I will argue that degrammaticalization is not grammaticalization in reverse, but a separate kind of change worthy of study in its own right. The purpose of this paper will be to show how degrammaticalization changes are best identified, by using existing linguistic tests as diagnostics for establishing changes in the morphological status of certain degrammaticalization suspects, and for assessing the nature of the subchanges involved. One of the stock examples of degrammaticalization literature, i.e. the s-genitive in Swedish, will serve as a case study.