It is well-known that grammatical movement is somehow linked to functional heads. There is less agreement on the excact nature of this correlation. According to one view, phrases are moved to the specifier positions of functional heads because functional heads attract them. According to another view, movement is not triggered by functional heads alone, but depends on the larger grammatical context. For instance, one such proposal says that T (tense) becomes attractive only when selected by finite C (complementizer), while V becomes attractive when selected by v* (transitivizer). What attracts phrases are therefore the C–T system and the v*–V system as a whole, not the individual functional heads; moved phrases are then sandwitched between the two heads. In this article, we present evidence in favor of this view by looking at first language acquisition. The data shows that in child Finnish, subject determiner phrases (DPs) move into the position of grammatical subject if and only if the full complementizer system has matured. Movement to the (Spec, TP) subject position therefore depends on the presence of C.