How to call a function within \umlcreatecall of tikz-uml

Question

I am using the tikz-uml package to make a uml sequence diagram and want to show what happens inside a constructor. Basically, I try to make a diagramm like this (source):

But instead, the constructor call ends to soon and doesn't act similar to an function call:

\documentclass{scrbook}

\usepackage{tikz}
\usepackage{tikz-uml}
\usepackage{float}

\begin{document}
    \begin{figure}[H]
        \begin{tikzpicture}
        \begin{umlseqdiag} 

        \umlobject[no ddots]{A}

        \begin{umlcreatecall}[dt=5,class=B]{A}{b}
            \begin{umlcreatecall}[dt=5,class=C]{b}{c}
            \end{umlcreatecall}
        \end{umlcreatecall}

        \end{umlseqdiag} 
        \end{tikzpicture}
    \end{figure}
\end{document}

Is this even possible with tikz-uml?