Problem with enumeration with an empty value

I have a WSDL containing this enumeration type

<xsd:simpleType name="item_type_enum">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="VCD"/>
<xsd:enumeration value="SVCD"/>
<xsd:enumeration value="CDAUDIO"/>
<xsd:enumeration value="DVD"/>
<xsd:enumeration value=""/><!-- can be an empty string -->
</xsd:restriction>
</xsd:simpleType>

Compiling a proxy i get this enumeration
item_type_enum.VCD
item_type_enum.SVCD
item_type_enum.CDAUDIO
item_type_enum.DVD
item_type_enum.Item
^^^^^^
Why the empty string becomes "Item"? I've tested it with webservice
studio ( http://tinyurl.com/2t8gd ). Composing the soap envelope it sends
the string "Item".
Is there something wrong in the WSDL? I just can't understand what
happens.

--
L'indirizzo di posta non è valido! Per contattarmi in privato usate il
form: http://www.gerry.it/serve/mail/
The mail address given is invalid, if you want to contact me, please use
this form instead: http://www.gerry.it/serve/mail/

Non so dire se cercassi qualcosa, o se fossi inseguito: ricordo che erano
tempi difficili ma io ero, per qualche strana ragione, felice. (S. Benni)