# Biblatex bibliography quotes break when using fontspec

As soon as I use fontspec in my biblatex xelatex document, my quotes stop appearing as proper quotes ", and start appearing as a pair of  and ''.

My minimal working example, first:

\documentclass{book}
\listfiles
\usepackage[stretch=10]{microtype}
\usepackage[quiet]{fontspec}
\usepackage[backend=biber]{biblatex}
\usepackage{hyperref}

\begin{document}
Hello world [\cite{Bonaini_Memoria}]

\printbibliography
\end{document


Everything looks good here:

then I add setmainfont:

\documentclass{book}
\listfiles
\usepackage[stretch=10]{microtype}
\usepackage[quiet]{fontspec}
\usepackage[backend=biber]{biblatex}
\usepackage{hyperref}

\setmainfont{Linux Libertine O}
\begin{document}
Hello world [\cite{Bonaini_Memoria}]

\printbibliography
\end{document}


and the thing breaks:

For completeness here is my bibliography biblatex entry:

@Article{Bonaini_Memoria,
author="Bonaini, F.",
title={Memoria unica sincrona di Leonardo Fibonacci novamente scoperta.},
journaltitle="Giornale Storico degli Archivi Toscani.",
date=1857,
volume="Vol. I.",
pages={239--246},
language={italian}


This seems a mystery to me! Any help would be greatly appreciated.

EDIT: What is weird, is if I take out the setmainfont directive, and instead usepackage{libertineotf} everything works great. :?

-

Putting \setmainfont[Mapping=tex-text]{Linux Libertine O} should be useful for this case.
In his answer Alan uses [Ligatures=TeX]. What is the advantage of using [Mapping=tex-text] or vise versa? –  drozzy Mar 9 '12 at 2:29
In fact Ligatures should be used instead, as per fontspec manual: but for consistency Ligatures=TeX will perform the same function as Mapping=tex-text. –  drozzy Mar 9 '12 at 2:31
[Mapping=tex-text] I believe was an old way of indicating that fontspec should replicate the typical ligature behavior of Latex. It is now the way that tells XeTeX to use these ligatures whereas Ligatures=TeX is for LuaTeX. Fontspec will work with Ligature=TeX when using XeTeX; I do not think th reverse is true. –  Amphipolis Mar 9 '12 at 19:51