[AUCTeX] Auctex breaks line when wrapped in environment

[Florian Lindner]

Hello,

when I have a line like this one:

This is a long line and it is not being broken by Emacs or by my, the author. 
And it should not be broken.

I mark the line and use C-c C-e to wrap in an environment it becomes:

\begin{center}
  This is a long line and it is not being broken by Emacs or by my,
  the author. And it should not be broken.
\end{center}

Auctex breaks the line. auto-fill-mode is disabled.

How can I disable that?

Thanks,
Florian