package.skeleton does invalide regular name...

Hi the list,

I am using package.skeleton on a file that has a very classic name, but 
package.skeleton detect it as a invalid name :

--- 8< -------
package.skeleton(name="packClassicBis",code_files="./packClassic/R/progClassic.R")

Cr?ation des r?pertoires...
Cr?ation de DESCRIPTION...
Cr?ation de 'Read-and-delete-me'...
Recopiage des fichiers de code...
Cr?ation des fichiers d'aide ...
Termin?.
Les ?tapes suivantes sont d?crites dans './packClassic4/Read-and-delete-me'.
Warning message:
In package.skeleton(name = "packClassic4", code_files = 
"./packClassic/R/progClassic.R") :
  Nom(s) de fichier(s) invalide(s) pour du code R ./packClassic4/R:
  'progClassic.R'
sont maintenant renomm?s vers 'z<nom>.R'
--- 8< -------

It create the file "zprogClassic.R" in directorie "packClassicBis\R"
Is there something wrong in my code or is it a bug in package.skeleton ?

Christophe