From early in development, race biases how children think about gender--often in a manner that treats Black women as less typical and representative of "women in general" than White or Asian women. The present study (N = 89, ages 7-11; predominately Hispanic, White, and multi-racial children) examined the generalizability of this phenomenon across middle childhood and the mechanisms underlying variability in its development. Replicating prior work, children were slower and less accurate to categorize the gender of Black women compared to Asian or White women, as well as compared to Black men, suggesting that children perceived Black women as less representative of their gender. These effects were robust across age within a racially and ethnically diverse sample of children. Children's tendencies to view their own racial identities as expansive and flexible, however, attenuated these effects: Children with more flexible racial identities also had gender concepts that were more inclusive of Black women. In contrast, the tendency for race to bias children's gender representations was unrelated to children's multiple classification skill and racial essentialism. These findings shed light on the mechanisms underlying variation in how race biases gender across development, with critical implications for how children's own identities shape the development of intergroup cognition and behavior.