Let $P$ and $Q$ be polynomials in one variable with complex coefficients and let $n$ be a natural number. Suppose that $Q$ is not constant and has only simple roots. Then there is a rational function $\varphi$ with ${\varphi }^{\text{'}}=P/Q^{n+1}$ if and only if the Wronskian of the functions $Q^{\text{'}},{\left(Q^2\right)}^{\text{'}},...,{\left(Q^n\right)}^{\text{'}},P$ is divisible by $Q$.