In this paper, grammatical blending is presented as an alternative to the conventional, linear overlap models of grammaticalization when it comes to conceptualizing complex cases of overlaps. The choice of the ‘emerging modal' want to/wanna as a case study is motivated precisely by its interpretational complexity. For it appears that the grammaticalization of want to/wanna has been shaped by the compositional interaction of form and meaning. In this configuration, the linear model has to be modified for two reasons: being exclusively semantic, it does not take the form of the expression into account; being linear, it does not lend itself to a treatment of constructional compositionality. Grammatical blending, understood as the blend of constructions as defined in the Construction Grammar framework, is one way of altering the linear model so as to enable the representation of non-linear (i.e. compositional) constructional overlaps.