Second language learners can destabilize and change the languages they acquire, due in part to competition between their first and second languages. There is reason to think that how one acquires a second language affects this competition. One such way of affecting language learning is feedback. In our preregistered study, 90 native English speakers learned and transmitted an artificial language with flexible word order and case marking across 15 iterated learning chains while receiving positive, negative, or no feedback. The original flexible word order remained most stable across generations of transmission when feedback was given; otherwise English SVO word order was likely to predominate by the final generation. These findings elucidate the role feedback may play in negotiating between competing linguistic variants and ensuring their stable transmission across generations.