This article reports on an investigation of changes in the grammatical competence of Germans living in the Netherlands. The participants (N = 52) were asked to give their judgments on the grammaticality of infinitive clauses in German. The judgments of this group were compared to those of a control group that lived in Germany and did not have contact with Dutch. The results revealed significant changes in the participants' L1, which indicate transfer from the cognate L2, Dutch. Furthermore, it could be demonstrated that L2-induced changes can occur after a relatively short period of time, at least in the case of cognate languages.