  Even dimensional defects and boundaries in conformal field theory support
type $a$ anomalies on their world-volume. We show that the one-point functions
of marginal operators, in the presence of defects and boundaries, are
anomalous, and that the Wess-Zumino consistency condition relates them to the
derivative of the $a$-anomaly with respect to the marginal coupling. We also
argue that the constant term $F$ for odd dimensional surfaces can depend on
marginal parameters.
