Previous studies report that exposure to the Maori language on a regular basis allows New Zealand adults who cannot speak Maori to build a proto-lexicon of Maori -- an implicit memory of word forms without detailed knowledge of meaning. How might this knowledge feed into explicit language learning? Is it possible to "awaken" the proto-lexicon in the context of overt language learning? We investigate whether implicit linguistic knowledge represented in a proto-lexicon gives any advantages for intentional language learning in a tertiary educational environment. We conducted a three-task experiment which: (a) assessed participants' Maori proto-lexicon; (b) assessed their phonotactic knowledge; and (c) tested them on Maori vocabulary that they had been exposed to during the course at two time points. The results show that students with larger Maori proto-lexicons learn more words in a classroom setting. This study shows that proto-lexicon acquired from ambient exposure can lead to significant benefits in language learning.