This article examines a 1779 legal dispute involving Pierre Chapuizet, a wealthy and well-connected sugar planter of the north province of Saint-Domingue who was denied a commission as an officer in the colonial militia due to allegations of mixed-race origin. Although the Conseil Superieur of Cap Francais had recognized Chapuizet's status as "white and unblemished" (blanc et ingenu) in 1771, the colonial administration and much of the white elite argued that his descent from a Black great-great-grandmother made him ineligible for the honor of a militia commission. This article argues that the Chapuizet affair demonstrates a shift in the boundaries of whiteness in the French Antilles. Traditional "color prejudice," in which skin color was one factor among many others, such as wealth and family connections, gave way to modern scientific racism defined by biological descent, according to which a single Black ancestor, however remote, sufficed for exclusion from the white elite.