Two comprehension experiments were conducted to investigate whether German children are able to use the grammatical cues of word order and word endings (case-markers) to identify agents and patients in a causative sentence, and whether they weigh these two cues differently across development. Two-year-olds correctly understood only sentences with both cues supporting each other – the prototypical form. Five-year-olds were able to use word order by itself, but not case-markers. Only seven-year-olds behaved like adults by relying on case-markers over word order when the two cues conflicted. These findings suggest that prototypical instances of linguistic constructions with redundant grammatical marking play a special role in early acquisition, and only later do children isolate and weigh individual grammatical cues appropriately.