  In their comment \cite{Sun} on our study of phonon heat transport in
Nd$_2$CuO$_4$ \cite{Li}, Sun and Ando estimate that the phonon mean free path
at low temperature is roughly half the width of the single crystal used in our
study, from which they argue that phonon scattering cannot be dominated by
sample boundaries. Here we show that their use of specific heat data on
Nd$_2$CuO$_4$, which contains a large magnetic contribution at low temperature
that is difficult to reliably extract, leads to an underestimate of the mean
free path by a factor two compared to an estimate based on the specific heat
data of the non-magnetic isostructural analog Pr$_2$CuO$_4$. This removes the
apparent contradiction raised by Sun and Ando.
