This paper is concerned with the acquisition of negative indefinites (NIs) by children who are acquiring English or German. In particular, it focuses on children's non-adult like productions of those indefinites where, like in languages that show negative concord, a sentential negator (not/n't or nicht) is realized in addition to the NI. Previous work on this matter investigating children's comprehension and adult artificial language learning indicate a bias towards negative concord. While the observed bias may result from negative concord being encoded in the grammar that children entertain at this point in their language development, it could equally well be explained by extra-grammatical factors, e.g. limited processing and pragmatic abilities. However, if we find sentences showing erroneous negative concord also in the productions of children acquiring English or German, we can more confidently claim that the observed bias is due to a phase in which negative concord is a proper part of their grammar. While there are reports of such productions, studies reporting them have limited validity due to their size and other confounds. We present results of an in-depth corpus study on several English- and German-acquiring children corroborating previous restricted findings. Our results show that children produce a substantial number of negative concord-like constructions during acquisition in both languages. However, we could not identify a particular negative concord phase. In addition, there are considerable quantitative and distributional differences between the two languages. We argue that these can be traced back to independent differences between English and German.