[standalone@localhost:9990 /] /subsystem=undertow/server=default-server/http-listener=default:write-attribute(name=max-connections, value=-20)

08:54:13,387 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-1) MSC000001: Failed to start service jboss.undertow.listener.default: org.jboss.msc.service.StartException in service jboss.undertow.listener.default: Failed to start service
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1919)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: High water must be greater than 0
	at org.xnio.nio.QueuedNioTcpServer.badHighWater(QueuedNioTcpServer.java:236)
	at org.xnio.nio.QueuedNioTcpServer.<init>(QueuedNioTcpServer.java:189)
	at org.xnio.nio.NioXnioWorker.createTcpConnectionServer(NioXnioWorker.java:200)
	at org.xnio.XnioWorker.createStreamConnectionServer(XnioWorker.java:243)
	at org.wildfly.extension.undertow.HttpListenerService.startListening(HttpListenerService.java:126)
	at org.wildfly.extension.undertow.ListenerService.start(ListenerService.java:167)
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1963)
	at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1896)
	... 3 more