doctrine-mapping.xsd does not allow for namespacing in discriminator-mapping element

The XSD type for the 'class' attribute in the 'discriminator-mapping' element is 'xs:NMTOKEN'. But this does not allow the '\' characters used for PHP namespacing. The 'type' should instead be changed to 'xs:string' as shown below:

<xs:complexType name="discriminator-mapping">
<xs:sequence>
<xs:any minOccurs="0" maxOccurs="unbounded" namespace="##other"/>
</xs:sequence>
<xs:attribute name="value" type="xs:NMTOKEN" use="required"/>
<xs:attribute name="class" type="xs:string" use="required"/>
<xs:anyAttribute namespace="##other"/>
</xs:complexType>