EJB deployer cannot be hot deployed

I tried to update the EJB timer service to use a new MySQLDS instead of DefaultDS. The service failed to redeploy correctly. I had to restart JBoss to make it come up cleanly. Here is the stack trace of the error on redeploy:

08:58:20,118 ERROR [EJBDeployer] Starting failed jboss.ejb:service=EJBDeployer
java.lang.IllegalArgumentException: Handler for key=javax.ejb.EnterpriseBean, exists, handler: org.jboss.ejb.plugins.EnterpriseBeanPolicyContextHandler@158638
at javax.security.jacc.PolicyContext.registerHandler(PolicyContext.java:170)
at org.jboss.ejb.EJBDeployer.startService(EJBDeployer.java:135)
at org.jboss.system.ServiceMBeanSupport.jbossInternalStart(ServiceMBeanSupport.java:272)
at org.jboss.system.ServiceMBeanSupport.jbossInternalLifecycle(ServiceMBeanSupport.java:222)
at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:141)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:80)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:72)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:249)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:644)
at org.jboss.system.ServiceController$ServiceProxy.invoke(ServiceController.java:911)
at $Proxy0.start(Unknown Source)
at org.jboss.system.ServiceController.start(ServiceController.java:416)
at sun.reflect.GeneratedMethodAccessor10.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:141)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:80)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:72)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:249)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:644)
at org.jboss.mx.util.MBeanProxyExt.invoke(MBeanProxyExt.java:177)
at $Proxy4.start(Unknown Source)
at org.jboss.deployment.SARDeployer.start(SARDeployer.java:273)
at org.jboss.deployment.MainDeployer.start(MainDeployer.java:964)
at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:775)
at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:738)
at sun.reflect.GeneratedMethodAccessor51.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:141)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:80)
at org.jboss.mx.interceptor.AbstractInterceptor.invoke(AbstractInterceptor.java:121)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:74)
at org.jboss.mx.interceptor.ModelMBeanOperationInterceptor.invoke(ModelMBeanOperationInterceptor.java:127)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:74)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:249)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:644)
at org.jboss.mx.util.MBeanProxyExt.invoke(MBeanProxyExt.java:177)
at $Proxy8.deploy(Unknown Source)
at org.jboss.deployment.scanner.URLDeploymentScanner.deploy(URLDeploymentScanner.java:325)
at org.jboss.deployment.scanner.URLDeploymentScanner.scan(URLDeploymentScanner.java:483)
at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.doScan(AbstractDeploymentScanner.java:204)
at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.loop(AbstractDeploymentScanner.java:215)
at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.run(AbstractDeploymentScanner.java:194)