Generated source files for nested simple enumeration type does not compile - "cannot find symbol org.apache.xmlbeans.XmlString.Enum"

Generated source files for xsd below does not compile:

***************************************************
<?xml version="1.0" encoding="ISO-8859-1" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:simpleType name="someAttributeType">
<xsd:restriction>
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="aaaaa" />
<xsd:enumeration value="bbbbb" />
<xsd:enumeration value="ccccc" />
<xsd:enumeration value="ddddd" />
<xsd:enumeration value="eeeee" />
</xsd:restriction>
</xsd:simpleType>
</xsd:restriction>
</xsd:simpleType>
<xsd:complexType name="SomeComplexType">
<xsd:attribute name="attr" type="someAttributeType"/>
</xsd:complexType>
</xsd:schema>
***************************************************

Compilation error message:
***************************************************
C:\projects\workspace-opensource\TestsForXmlBeansBugs\.\srcgen\noNamespace\SomeComplexType.java:24: cannot find symbol
symbol : class Enum
location: interface org.apache.xmlbeans.XmlString
org.apache.xmlbeans.XmlString.Enum getAttr();
.... and so on
***************************************************

Xsd file is valid according to http://www.w3.org/2001/03/webdata/xsv validator.
One may ask if it makes sense - unfortunately I must work with a schema with similiar constructs:
http://crd.gov.pl/xml/schematy/adres/2008/05/09/adres.xsd

This problem occurs in xmlbeans 2.4.0 (there is no such a version to choose when creating bug so I've chosen TBD) and current trunk from svn repo.