  We present a generalization of the infinitesimal gauge transformation for
nonabelian fields on the stack of branes up to the third order in $\Phi$. We
test the gauge invariance of the action up to the fifth order in $\Phi$ for
$D$-instantons. This substantiates the Myers formula for the Chern-Simons term
in action, which describes interaction with the RR fields of $N$ coincident
$\Dp$ branes.
