Let $f:M\to M$ be a $C^{1+\alpha}$ diffeomorphism of a compact Riemannian manifold, with $\alpha>0$, and let $\mu$ be an ergodic hyperbolic invariant probability measure whose conditional measures on unstable manifolds are absolutely continuous with respect to the induced Riemannian volume. Then
\begin{align*}
h_\mu(f)=\sum_{\lambda_i>0}m_i\lambda_i.
\end{align*}