Custom workmanager leads to ERROR

        <subsystem xmlns="urn:jboss:domain:jca:1.1">
            <archive-validation enabled="false"/>
            <bean-validation enabled="false"/>
            <default-workmanager>
                <short-running-threads blocking="true">
                    <core-threads count="10" per-cpu="20"/>
                    <queue-length count="10" per-cpu="20"/>
                    <max-threads count="10" per-cpu="20"/>
                    <keepalive-time time="10" unit="seconds"/>
                </short-running-threads>
            </default-workmanager>
            <workmanager name="Custom">
                <short-running-threads blocking="true">
                    <core-threads count="10" per-cpu="20"/>
                    <queue-length count="10" per-cpu="20"/>
                    <max-threads count="10" per-cpu="20"/>
                    <keepalive-time time="10" unit="seconds"/>
                </short-running-threads>
            </workmanager>
            <bootstrap-contexts>
              <bootstrap-context name="Custom" workmanager="Custom"/>
            </bootstrap-contexts>
        </subsystem>

10:08:40,914 ERROR [org.jboss.as.controller] (ServerService Thread Pool -- 38) JBAS014612: Operation ("add") failed - address: ([
    ("subsystem" => "jca"),
    ("workmanager" => "Custom"),
    ("short-running-threads" => "short-running-threads")
]): org.jboss.msc.service.DuplicateServiceException: Service jboss.thread.executor.short-running-threads.thread-factory is already registered
        at org.jboss.msc.service.ServiceRegistrationImpl.setInstance(ServiceRegistrationImpl.java:154) [jboss-msc-1.0.1.GA.jar:1.0.1.GA]
        at org.jboss.msc.service.ServiceControllerImpl.startInstallation(ServiceControllerImpl.java:226) [jboss-msc-1.0.1.GA.jar:1.0.1.GA]
        at org.jboss.msc.service.ServiceContainerImpl.install(ServiceContainerImpl.java:560) [jboss-msc-1.0.1.GA.jar:1.0.1.GA]
        at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:201) [jboss-msc-1.0.1.GA.jar:1.0.1.GA]
        at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2211) [jboss-msc-1.0.1.GA.jar:1.0.1.GA]
        at org.jboss.msc.service.ServiceBuilderImpl.install(ServiceBuilderImpl.java:307) [jboss-msc-1.0.1.GA.jar:1.0.1.GA]
        at org.jboss.as.controller.OperationContextImpl$ContextServiceBuilder.install(OperationContextImpl.java:843) [jboss-as-controller-7.1.0.Alpha2-SNAPSHOT.jar:7.1.0.Alpha2-SNAPSHOT]
        at org.jboss.as.threads.ThreadsSubsystemThreadPoolOperationUtils.addThreadFactoryDependency(ThreadsSubsystemThreadPoolOperationUtils.java:64)
        at org.jboss.as.threads.BoundedQueueThreadPoolAdd.performRuntime(BoundedQueueThreadPoolAdd.java:105)
        at org.jboss.as.controller.AbstractAddStepHandler$1.execute(AbstractAddStepHandler.java:50) [jboss-as-controller-7.1.0.Alpha2-SNAPSHOT.jar:7.1.0.Alpha2-SNAPSHOT]
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:327) [jboss-as-controller-7.1.0.Alpha2-SNAPSHOT.jar:7.1.0.Alpha2-SNAPSHOT]
        at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:221) [jboss-as-controller-7.1.0.Alpha2-SNAPSHOT.jar:7.1.0.Alpha2-SNAPSHOT]
        at org.jboss.as.controller.AbstractOperationContext.completeStep(AbstractOperationContext.java:157) [jboss-as-controller-7.1.0.Alpha2-SNAPSHOT.jar:7.1.0.Alpha2-SNAPSHOT]
        at org.jboss.as.controller.ParallelBootOperationStepHandler$ParallelBootTask.run(ParallelBootOperationStepHandler.java:294) [jboss-as-controller-7.1.0.Alpha2-SNAPSHOT.jar:7.1.0.Alpha2-SNAPSHOT]
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [:1.6.0_25]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [:1.6.0_25]
        at java.lang.Thread.run(Thread.java:662) [:1.6.0_25]
        at org.jboss.threads.JBossThread.run(JBossThread.java:122) [jboss-threads-2.0.0.GA.jar:2.0.0.GA]