[Tex/LaTex] Fixing an overfull box

Question

I have an overfull box in a French text which looks like this:

The sequence at the end of the line is:

d'Ananias~: \og Vous

"Vous" cannot be hyphenated and \og inserts a non-secable space, so the only place where it could be cut is after the colon.

I'm using XeTeX with microtype (2.5 beta6 for XeTeX support). How can I fix this overfull box?

Do I have to allow lines to stretch more (and how)?

Answer 1

The link Overfull gives "More satisfactory is to make small changes to \tolerance, incrementally, and then to look to see how the change affects the result; very small increases can often do what’s necessary."

%!TEX TS-program = xelatex
\documentclass[draft,12pt]{article} 
\usepackage{fontspec} 
\usepackage{xunicode}
\usepackage{lmodern} 
\usepackage[textwidth=13cm]{geometry} 
\usepackage[french]{babel}

\usepackage[protrusion = true,
            final]{microtype}    

\begin{document}

%\tolerance=270
  Voici l'accusation que Pierre a formulée à l'encontre d'Ananias: \og Vous avez menti à l'Esprit-Saint. \fg{} Il est également possible de blasphémer contre le Ciel, contre les saints, contre la vertu.

\end{document}

With \tolerance=270

I think expansion does not work with xelatex