[XeTeX] no sukun for some words with arabxetex

[drrd drrd]

Hello,
Sorry if this subject is not new, but I don't find any response in the forums.
When i use arabxetex with xelatex and when i want to show all sukuns with fullvoc mode, some sukun don't appear. In this example, the sukuns doesn't appear. It seems thas letter "waw" after a sukun create a problem.
Maybe someone could help me about this problem.
Thank you.
Source code :
\documentclass[a4paper,10pt]{article}
\usepackage{fontspec,xltxtra,xunicode}
\usepackage{arabxetex}
\usepackage[french]{babel}
\begin{document}
\begin{arab}[fullvoc]

`anwaTaN, na.hwa, tamwIlu

\end{arab}
\end{document}

 		 	   		  
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