Unable to override load properties when running in Tomcat 6

  <Listener className="org.jboss.modcluster.ModClusterListener" 
	loadMetricClass="org.jboss.modcluster.load.metric.impl.BusyConnectorsLoadMetric"
	loadMetricCapacity="1" />

Apr 19, 2011 4:13:26 PM org.apache.tomcat.util.IntrospectionUtils setProperty
WARNING: IAE org.jboss.modcluster.ModClusterListener@739e8329 loadMetricCapacity 5
java.lang.IllegalArgumentException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.tomcat.util.IntrospectionUtils.setProperty(IntrospectionUtils.java:334)
	at org.apache.tomcat.util.IntrospectionUtils.setProperty(IntrospectionUtils.java:262)
	at org.apache.tomcat.util.digester.SetPropertiesRule.begin(SetPropertiesRule.java:208)
	at org.apache.tomcat.util.digester.Rule.begin(Rule.java:153)
	at org.apache.tomcat.util.digester.Digester.startElement(Digester.java:1356)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
	at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(AbstractXMLDocumentParser.java:179)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1343)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2755)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
	at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
	at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1642)
	at org.apache.catalina.startup.Catalina.load(Catalina.java:524)
	at org.apache.catalina.startup.Catalina.load(Catalina.java:562)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.catalina.startup.Bootstrap.load(Bootstrap.java:261)
	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)