# opening brace alignment/indentation problem in LaTeX mode

I have an alignment/indentation problem in LaTeX mode. Every time I begin a line with an opening brace and I hit <TAB> or run an indentation command on the region, the brace becomes aligned with the previous opening brace, even if a closing brace has been inserted in between. For instance,

\begin{document}
{\foo}


becomes

\begin{document}
{\foo}


Because of this, the document is increasingly shifted to the right. How can I get rid of this behavior? I use GNU Emacs 24.5.1. I have tried to open the LaTex file with emacs -q --no-site-file to make sure this is not due to a local configuration file, to no avail...