Size-luminosity diagram of a sample of Herbig Ae/Be stars (adopted from Monnier et al. 2005). The K-band ring-fit radius of V921 Sco determined in this paper is plotted as a red triangle. The dotted blue lines represent model curves for three different dust sublimation temperatures. The plotted red error bar represents the parameter uncertainty reported in Borges Fernandes et al. (2007), but the total uncertainty is probably larger.