Has anybody ever heard about this theorem? $L\{f'(t)\}(0)+f(0)=k$

Question

Does anybody know the following theorem?

$y(0)+f(0)=k$.

Let $f:D\rightarrow C$ be a Laplace function with additional constant $k$, and $y(s)=L\{f'(t)\}$. If $y(0)$ is defined then:

$y(0)+f(0)=k$.