# TikZ: wrong edge between split rectangles in graphs

Consider the following minimal example:

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{graphs,graphdrawing,shapes.multipart}
\usegdlibrary{trees}

\begin{document}
\tikz[every node/.style={rectangle split,rectangle split parts=2,draw}]{
\graph[tree layout,grow=0] {
a/a\nodepart{two}1;
b/b\nodepart{two}2;
c/c\nodepart{two}3;
a -- {b, c};
};
}
\end{document}


The result (with PGF 3.0.1) is:

There is an incorrect edge in the sense that the line corresponding to a -- c does not stop at the edge of node a. Is this a bug or intended? How could I work around it?

It seems to be, because the boxes are transparent. I tried this:

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{graphs,graphdrawing,shapes.multipart}
\usegdlibrary{trees}

\begin{document}
\tikz[every node/.style={rectangle split,rectangle split parts=2,draw, fill=white}]{
\graph[tree layout,grow=0] {
a/a\nodepart{two}1;
b/b\nodepart{two}2;
c/c\nodepart{two}3;
a -- {b, c};
};
}
\end{document}