In this paper, we propose a ‘constructionist’ scenario of grammaticalization that links successive diachronic stages of a grammaticalization process with particular construction types. Relying on earlier work, especially on the model of relevant context types in grammaticalization proposed in Diewald (2002), we develop the model further and introduce an additional developmental stage into the model, i.e. the stage of paradigmatic (re-)integration. This fourth stage restricts the model to grammaticalization processes and sharpens the notion of grammaticalization. In particular, we advocate the view that the fourth stage can and must be formulated as an essential criterion for differentiating grammaticalization from lexicalization and from other types of semantic change.