[XeTeX] Problem with Turkish dotted I (U+0130) in headers

[Alessandro Ceschini]

In a document like this:*
****
***

    |\documentclass*[*|*|a4paper, 12p|*|t]{boo|*|k}
    \usepackage{fancyhdr}
    \pagestyle{fancy}
    \usepackage{fontspec}
    \defaultfontfeatures{Language=Turkish, Mapping=tex-text}
    \setmainfont{Linux Libertine G}
    \usepackage{polyglossia}
    \setmainlanguage{turkish}
    \usepackage{xunicode}
    \usepackage{xltxtra}
    \usepackage{bookmark}
    \usepackage{epigraph}

    \begin{document}

    \chapter{Birinci}

    \section{İkinci}

    \end{documen|*|t||}|
*
*

**Now, what's in the header is small caps, right? So, it gets 
capitalized, but the problem is that "i" gets capitalized in Turkish as 
dotted I, that is: "İ" (U+0130) and this, XeLaTeX doesn't do. Is there a 
way to enjoin it to do so?

**
-- 
Alessandro Ceschini