xemacs: Unable to load any usable fontset

If running XEmacs causes these warnings about fonts:

[jerome@mathusalem] > xemacs
Warning: Missing charsets in String to FontSet conversion
Warning: Cannot convert string "-*-helvetica-bold-r-*-*-*-120-*-*-*-*-iso10646-1,                               -*-helvetica-bold-r-*-*-
*-120-*-*-*-*-iso8859-*,                                *" to type FontSet
Warning: Missing charsets in String to FontSet conversion
Warning: Unable to load any usable fontset
Warning: Missing charsets in String to FontSet conversion
Warning: Unable to load any usable fontset

Then, try running it this way:

[jerome@mathusalem] > LANG=C xemacs