Abstract Contraction of want to to wanna is sometimes possible (e.g., Who do you want to/wanna stay with ___ ? ), but sometimes impossible (e.g., Who do you want ___ to/*wanna stay? ). This contrast is attributable to the grammatical constraint that a wh -trace blocks the contraction of want and to . Most first language (L1) and second language (L2) acquisition studies testing learner knowledge of this constraint have used elicited production tasks and focused on adult participants, with inconsistent results. Using a child-friendly acceptability judgment task, the current study shows that children as young as 3;11 and both child and adult L2 learners have target-like knowledge of the constraint on wanna contraction. This result is in line with the position that L1 acquisition, child L2 acquisition, and adult L2 acquisition are qualitatively similar.