This study extended an existing crosslinguistic model of verb-marking errors in children's early multiword speech (MOSAIC) by adding a novel mechanism that defaults to the most frequent form of the verb where this accounts for a high proportion of forms in the input. Our simulations showed that the resulting model not only provides a better explanation of the data on typically developing children but also captures the crosslinguistic pattern of verb-marking error in children with developmental language disorder, including the tendency of English-speaking children to show higher rates of optional-infinitive errors and the tendency of Dutch-, German-, and Spanish-speaking children to show higher rates of agreement errors. The new version of MOSAIC thus provides a unified crosslinguistic model of the pattern of verb-marking errors in typically developing children and children with developmental language disorder.