Spacing/newline issue for \numberstringnum in polyglossia german

[Vidabe]

The following example using xelatex/lualatex

\documentclass{article}
\usepackage{polyglossia}
\setmainlanguage{german}
\usepackage{fmtcount}
\begin{document}
a\Numberstringnum{2}b
\end{document}

creates a break between "a" and "b"