On Cauchy type integrals in domains with smooth boundary

There exist a Jordan domain $G$ with $C^1$-boundary and a Cauchy integral $f$ in $G$ such that $(f\circ\varphi)\varphi'$ is not a Cauchy integral in the unit disc $\mathbb D$, $\varphi$ being a conformal map of $\mathbb D$ onto $G$.