Since early studies in language development, scholars have noticed that function words, in particular auxiliaries, often appear to be missing in early speech, with the result that child utterances sometimes exhibit verbs with non-finite morphology in seemingly matrix clauses. This has led to the idea of a ‘deficit’ in the child's syntactic representations. In contrast with previous studies, this article explores the possibility that the child's phonology may considerably impact her overt realization of auxiliaries. Specifically, it examines the hypothesis that non-finite verbs in early speech are in fact attempted periphrastics (i.e. auxiliary/modal+non-finite verb) in which the auxiliaries are just reduced phonetically, often to the point where they remain unpronounced. We studied 28 normally developing French-speaking children aged between 23 and 37 months. New observational data uncovered a continuum in a given child's phonetic realizations of auxiliaries. Children showed various levels of auxiliary reduction, suggesting that their non-finite verbs are best analyzed as being part of periphrastics involving an auxiliary form that represents the endpoint on this continuum, i.e. is (completely) deleted. Further examination of these verbs revealed that their semantics corresponds to the semantics of adult periphrastics. Additionally, the results of an experiment where children imitated sentences with either periphrastic or synthetic verbs showed that responses with non-finite verbs were predominantly produced when the target sentence involved a periphrastic, rather than a synthetic verb.