diff --git a/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java b/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java
index 95fcfea142fb..be00b41d00c6 100644
--- a/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java
+++ b/jetty-core/jetty-http/src/test/java/org/eclipse/jetty/http/HttpURITest.java
@@ -1109,6 +1109,8 @@ public static Stream<Arguments> concatNormalizedURICases()
             Arguments.of("hTTps", "example.org", 443, "/", null, null, "https://example.org/"),
             Arguments.of("WS", "example.org", 8282, "/", null, null, "ws://example.org:8282/"),
             Arguments.of("wsS", "example.org", 8383, "/", null, null, "wss://example.org:8383/"),
+            // Undefined scheme
+            Arguments.of(null, "example.org", 8181, "/", null, null, "//example.org:8181/"),
             // Undefined Ports
             Arguments.of("http", "example.org", 0, "/", null, null, "http://example.org/"),
             Arguments.of("https", "example.org", -1, "/", null, null, "https://example.org/"),
diff --git a/jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/Request.java b/jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/Request.java
index 0673d9160167..aa494c761ec1 100644
--- a/jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/Request.java
+++ b/jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/Request.java
@@ -486,9 +486,13 @@ static int getServerPort(Request request)
             return authority.getPort();
 
         // Is there a scheme with a default port?
-        HttpScheme scheme = HttpScheme.CACHE.get(request.getHttpURI().getScheme());
-        if (scheme != null && scheme.getDefaultPort() > 0)
-            return scheme.getDefaultPort();
+        String rawScheme = uri.getScheme();
+        if (StringUtil.isNotBlank(rawScheme))
+        {
+            HttpScheme scheme = HttpScheme.CACHE.get(rawScheme);
+            if (scheme != null && scheme.getDefaultPort() > 0)
+                return scheme.getDefaultPort();
+        }
 
         // Is there a local port?
         SocketAddress local = request.getConnectionMetaData().getLocalSocketAddress();