[OS X TeX] Fontspec + muticols

[Jacques ANDRÉ]

I have the following program on TeXShop :

%!TEX encoding = UTF-8 Unicode
\documentclass{article}
\usepackage{multicol}
\usepackage{fontspec}
\usepackage{makeidx} 
\makeindex
\begin{document} % 
aaaa\index{aaa}
\begin{multicols}{3}
bbb
\printindex
\end{multicols}
\end{document}

I successfully run it with Lualatex
then I successfully run it with makeindex
then, if I try to run it with lualatex again, I must abort it for it loops (infinite number of output pages)

If i delete the \usepackage{fontspec} OR if I comment the \begin{multicols}{3} and \end{multicols} lines  , it works.

Why?

Jacques André