  We compute change in entanglement entropy for a single interval in $1+1$
dimensional sine-Gordon model perturbatively in the coupling. The sine-Gordon
perturbation can be thought of as deformation of the free CFT by a primary
operator with dimension $\Delta$. In an independent computation we calculate
holographic entanglement entropy for that interval from three dimensional bulk
AdS which has a massive scalar with its mass satisfying $m^2=
\Delta(\Delta-2)$. We show that the two results match for near-marginal
perturbations upto leading order in the coupling.
