  We study the light rays in a static and spherically symmetric gravitational
field of null aether theory (NAT). To this end, we employ the Gauss-Bonnet
theorem to compute the deflection angle by a NAT black hole in the weak limit
approximation. Using the optical metrics of the NAT black hole, we first obtain
the Gaussian curvature and then calculate the leading terms of the deflection
angle. Our calculations show how gravitational lensing is affected by the NAT
field. We also show once again that the bending of light stems from a global
and topological effect.
