Zero width no-break space (U+FEFF) in clearsigned output message

[lusfert]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: RIPEMD160

Hi all.

I wrote some text (with non-ASCII characters) in file encoded in UTF-8
with BOM and save it.
Then I decided to clearsign it:

gpg --verbose -u 0x500B8987 --clearsign 1.txt

When I open clearsigned 1.txt.asc I can find symbol U+FEFF (Zero width
no-break space) before message, but after field "Hash:". Adding option
- -t does not change anything. But if source file is encoded in UTF-8
without BOM, character U+FEFF doesn't appear in output clearsigned text.

Why does symbol "zero width no-break space" appear if source file has
Unicode signature (BOM)?

Configuration: GnuPG 1.4.2 official build, WinXP Pro SP2, standard cmd.exe

Regards

- --
Current OpenPGP key ID: 0x500B8987
Key fingerprint: E883 045D 36FB 8CA3 8D69  9C79 9E35 3B56 500B 8987
Encrypted e-mail preferred.

-----BEGIN PGP SIGNATURE-----

iD8DBQFDiHjYnjU7VlALiYcRAy2RAKCPvZ2MNSD3/SxExNrqZqqyKplljQCgkV9i
pP2KweQ1wvUI6ZHWo2M+CkM=
=N/yE
-----END PGP SIGNATURE-----