subgraph's border line is not drawn

[pstwo]

I have some issue with subgraph. I have to use node attribute, like `node [shape=box]', to get the border of subgraph drawn.

The situation is worse with Chinese characters; the attribute does not help any more. But when remove one Chinese character from node name ``三四五'' the border shows again.

Below is a test tex file with three cases. I tried dot and it draw subgraph border in each case.

\documentclass{article}
\usepackage{ctex}
\usepackage{tikz}
\usetikzlibrary{arrows,shapes}
\usepackage{dot2texi}

\begin{document}
% G's subgraph border line is not drawn
\begin{dot2tex}
graph G {
	OneTwo -- ThreeFourFive
	subgraph cluster_T {
		Hello -- World
	}
}
\end{dot2tex}
% H's subgraph border line is not drawn
\begin{dot2tex}
graph H {
	node [shape=box]
	一二 -- 三四五
	subgraph cluster_T {
		你好 -- 世界
	}
}
\end{dot2tex}
% I's subgraph border line is drawn
\begin{dot2tex}
graph I {
	node [shape=box]
	一二 -- 三四
	subgraph cluster_T {
		你好 -- 世界
	}
}
\end{dot2tex}
\end{document}