Wrong names for theorems/lemma/etc. in LyX

Wrong names for theorems/lemma/etc. in LyX

I am using LyX 2.0.3, and I usually type my documents (my lecture notes, mainly) in french.
Now, I have to write a paper in english, I can't get the label names of the AMS Theorems package to be in english and not in french. They appear in french in the user interface (which, I guess, is the normal behavior), but in english in the PDF. This is weird, because:
the language of my document is setup as « English »,
the language pack option in « Documents parameters » → « Language » is « Automatic » (but I have tried all the other options and none is working),
and LyX automatically uses babel.
When I export in LaTeX, the following lines are added :
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands.
\theoremstyle{plain}
\newtheorem{thm}{Théorème}
  \theoremstyle{definition}
  \newtheorem{defn}[thm]{Définition}
  \theoremstyle{remark}
  \newtheorem*{rem*}{Remarque}
  \theoremstyle{plain}
  \newtheorem{cor}[thm]{Corollaire}
  \theoremstyle{plain}
  \newtheorem{prop}[thm]{Proposition}
  \theoremstyle{plain}
  \newtheorem{fact}[thm]{Fait}
I do not know what adds them. If I manually replace them by their english equivalent, it works fine. So, is there a better solution than to systematically add all the correct definitions in the preambule? Additionally, should I send a bug report to the Lyx developers?