[undertow-dev] SSL Proxying

I'm using Undertow 1.4.20.Final and attempting to proxy an SSL connection to another Undertow server (also running 1.4.20.Final). However, I'm getting the following error: error: Sep 14, 2017 1:25:29 PM io.undertow.server.handlers.proxy.ProxyHandler handleFailure error: ERROR: UT005028: Proxy request to /drive failed error: java.io.IOException: UT001000: Connection closed error: at io.undertow.client.http.HttpClientConnection$ClientReadListener.handleEvent(HttpClientConnection.java:578) error: at io.undertow.client.http.HttpClientConnection$ClientReadListener.handleEvent(HttpClientConnection.java:516) error: at org.xnio.ChannelListeners.invokeChannelListener(ChannelListeners.java:92) error: at org.xnio.conduits.ReadReadyHandler$ChannelListenerHandler.readReady(ReadReadyHandler.java:66) error: at org.xnio.nio.NioSocketConduit.handleReady(NioSocketConduit.java:88) error: at org.xnio.nio.WorkerThread.run(WorkerThread.java:561) I've done this in earlier versions of Undertow and it didn't have any trouble, and I don't think the code has changed. I'm using the same certificate on both the proxy and the internal server. Unfortunately this error gives me very little information to diagnose the problem. Any suggestions are appreciated. Thanks, Matt