diff --git a/dd-java-agent/instrumentation/undertow/undertow-common/src/main/java/datadog/trace/instrumentation/undertow/HttpServerExchangeURIDataAdapter.java b/dd-java-agent/instrumentation/undertow/undertow-common/src/main/java/datadog/trace/instrumentation/undertow/HttpServerExchangeURIDataAdapter.java
index a9dbc130978..947dcefb887 100644
--- a/dd-java-agent/instrumentation/undertow/undertow-common/src/main/java/datadog/trace/instrumentation/undertow/HttpServerExchangeURIDataAdapter.java
+++ b/dd-java-agent/instrumentation/undertow/undertow-common/src/main/java/datadog/trace/instrumentation/undertow/HttpServerExchangeURIDataAdapter.java
@@ -22,7 +22,13 @@ public String host() {
 
   @Override
   public int port() {
-    return httpServerExchange.getHostPort();
+    try {
+      return httpServerExchange.getHostPort();
+    } catch (final NullPointerException e) {
+      // Undertow's getHostPort() can NPE internally (e.g. no Host header and a connection whose
+      // local address isn't an InetSocketAddress, such as AJP or a Unix domain socket transport).
+      return 0;
+    }
   }
 
   @Override