  The $B\to \gamma \ell \nu_\ell$ decay at large energies of the photon
receives a numerically important soft-overlap contribution which is formally of
the next-to-leading order in the expansion in the inverse photon energy. We
point out that this contribution can be calculated within the framework of
heavy-quark expansion and soft-collinear effective theory, making use of
dispersion relations and quark-hadron duality. The soft-overlap contribution is
obtained in a full analogy with the similar contribution to the $\gamma^*
\gamma \to \pi$ transition form factor. This result strengthens the case for
using the $B\to \gamma \ell \nu_\ell$ decay to constrain the $B$-meson
distribution amplitude and determine its most important parameter, the inverse
moment $\lambda_B$.
