File name error with diacritic

I create a sound recording with diacritic in file name (fermé). After confirmation, the sound does not appear in list, so I create another file with other name (close). But when I need to reboot the pbx, Asterisk failed to restart with a file not found error. The displayed file name was ferm?.
I delete the two file created with a wrong name and then Asterisk restart.
So you must forbid this kind of file name or correct the bug with corrupted file name.
Regards.