Spring ref vs. bean: no ID/IDREF binding for IDREF

hen upgrading a project from Mule 1.x to Mule 2.x, I ran into the following error while converting my Mule configuration file:

A Fatal error has occurred while the server was running:
cvc-id.1: There is no ID/IDREF binding for IDREF 'someProxy'.
(org.xml.sax.SAXParseException)

The offending bean:

   <spring:bean id="myImplementationBean" class="org.my.class" scope="prototype">
      <spring:property name="myInterface">
        <spring:ref local="myProxy"/>
      </spring:property>
    </spring:bean>

The problem was using local instead of bean as the value of the spring:property:

   <spring:bean id="myImplementationBean" class="org.my.class" scope="prototype">
      <spring:property name="myInterface">
        <spring:ref bean="myProxy"/>
      </spring:property>
    </spring:bean>

For a discussion the difference, see Spring-ref-local-vs-ref.