Polyglossia and Biblatex - Changing local variables

I m using Biblatex with polyglossia and although I set german as my default language, the bibliography shortcuts are still in english. Here is a minimal working example:

\begin{filecontents*}{literatur.bib}

@article{Grothendieck,
author = {Grothendieck, A.},
title = {Sur quelques points d'algebre homologique, I},
language = {fr},
journal = {Tohoku Mathematical Journal},
volume = {9},
year = {1957},
pages = {119-221},
}
\end{filecontents*}

\documentclass{article}
\usepackage[babelshorthands]{polyglossia}
\setdefaultlanguage[spelling=new,latesthyphen=true]{german}
\usepackage[style=alphabetic,backend=biber,maxnames=5,maxalphanames=5,backref=true,backrefstyle=two+]{biblatex}
\renewbibmacro{in:}{}
\DefineBibliographyStrings{german}{%
backrefpage = {zit. auf S.},
backrefpages = {zit. auf S.},
}
\bibliography{literatur}

\begin{document}
This is a citation of \cite{Grothendieck}.
\printbibliography
\end{document}


With this I get "pp." instead of "S." and "cit. on p." instead of "zit. auf S.". How can I fix that? Thanks in advance.

-
Joseph Wright of the biblatex team has just worked out why the polyglossia support didn't work properly. I have just incorporated his fix into the biblatex 2.8 DEV version on SF if you would like to try it (and leave a comment on the github issue for this - github.com/plk/biblatex/issues/69) –  PLK Sep 28 '13 at 12:55

biblatex has removed the support for polyglossia (probably because of a bug which appeared some time ago). Either use \usepackage[ngerman]{babel} (it will work fine with XeLaTeX/luaLaTeX), or use language=german in the options of biblatex.