[AUCTeX] Auctex and master files

[Damian]

Hello,

I have the following variables at the endo of a tex file:
%%% Local Variables:
%%% mode: pdflatex
%%% TeX-master: "main"
%%% End:

However, when I issue the compile (C-c C-c RET Latex RET) command, the
current file is compiled instead of main, that is, I got the following
error:
ERROR: LaTeX Error: Missing \begin{document}.

I've tried reloading Auctex (C-c C-n), but I still got the same
problem. Sorry if I miss something for the manual, but I don't know
how to solve this problem.

Thanks in advance,
Damian.