A New Term in Type II Effective Action

We show that the one loop effective action of type IIA and IIB string theories in ten dimensions have terms proportional to the dilaton times the ten dimensional Euler density, in apparent violation of the soft dilaton theorem. This can be traced to the existence of the zero modes of the world-sheet superconformal ghost fields and resolves a puzzle that arose recently in the analysis of black hole index when we compactify these theories on Calabi-Yau manifolds of non-zero Euler number.