This paper examines two types of light-verb constructions in Ndebele, which differ in the form of the main, lexical verb (participle vs subjunctive). I argue, against existing approaches, that main verb morphology in those constructions is not an idiosyncratic property of individual light verbs, but that it falls out from their syntax; in particular, from the light verb's nature as a functional or a lexical verb. Functional verbs have a valued Infl-feature and enter in a direct agree relation with the main verb, assigning a participial form. Lexical light verbs do not have a valued Infl-feature and therefore cannot provide an Infl-value to the main verb. I propose that the subjunctive form is a morphological reflex of a syntactic configuration where direct valuation cannot obtain. The view of verbal forms such as participle and subjunctive is, then, treated as a configurational phenomenon, and subjunctive morphology as a reflex of the inflectional deficiency of its immediate syntactic context.