  In order to compute the entanglement entropy for a given region in a theory
with an Einstein gravity dual, the Ryu-Takayanagi prescription tells us that we
must compute the the area of an extremal surface anchored to the entangling
region. However, if the dual gravity theory receives higher-curvature
corrections we are compelled to extremize a quantity which is no longer given
by the area but a higher-derivative functional. Hence, in order to find the
extremal surface that yields the correct value of the entanglement entropy, we
must include an additional boundary condition to the problem. We claim that the
additional condition can be fixed by demanding that the relationship between
the bulk depth and the size of the entangling region is the one induced by
geodesics, we call this the free-kick condition. We implement this prescription
in the computation of the entanglement entropy of the hairy black hole in new
massive gravity, and find a perfect agreement with conformal field theory
expectations.
