Written French is known as a deep orthography, presenting important differences between the spoken and written language systems, especially as far as morphology is concerned. This exploratory study of subject-verb agreement in number illustrates the long and laborious differentiation process of spoken and written French in child learners. The focus of the study is the L2 child, who learns to speak and write in the L2 more or less simultaneously. In a multiple case study, the written production of Swedish child L2 learners of French is compared to that of age-matched L1 children. The results demonstrate that while child L1 writers are strongly biased towards spoken language, the child L2 writers studied here are not yet able to take full advantage of either the spoken or the written language systems when writing in French.