Indexing a content in fr_BE seems to not allow to search for it

When creating a document in french (belgian) language in a multilingual wiki supporting english, fr, fr_BE seems to make the french belgian content not searchable.

1/ Create a document with the following content:

Voici un contenu en français.. Avec un mot au pluriel: voiliers Un autre contenu..

2/ Set the document in fr_BE

3/ Search for "voiliers".. Nothing shows up.

4/ Set the document in fr

5/ Search for "voiliers".. result shows up.