diff --git a/example/main.go b/example/main.go
index d29097de..9f53b5f9 100644
--- a/example/main.go
+++ b/example/main.go
@@ -144,7 +144,6 @@ func main() {
 	flag.Var(&bs, "bind", "bind to")
 	www := flag.String("www", "", "www data")
 	tcp := flag.Bool("tcp", false, "also listen on TCP")
-	customAltSvcPort := flag.Uint("customAltSvcPort", 0, "use custom Alt-Svc header port value")
 	enableQlog := flag.Bool("qlog", false, "output a qlog (in the same directory)")
 	flag.Parse()
 
@@ -183,12 +182,7 @@ func main() {
 			var err error
 			if *tcp {
 				certFile, keyFile := testdata.GetCertificatePaths()
-				if *customAltSvcPort != 0 {
-					logger.Infof("using customAltSvcPort = %v", *customAltSvcPort)
-					err = http3.ListenAndServeWithCustomAltSvcPort(bCap, certFile, keyFile, handler, uint32(*customAltSvcPort))
-				} else {
-					err = http3.ListenAndServe(bCap, certFile, keyFile, handler)
-				}
+				err = http3.ListenAndServe(bCap, certFile, keyFile, handler)
 			} else {
 				server := http3.Server{
 					Server:     &http.Server{Handler: handler, Addr: bCap},
diff --git a/http3/server.go b/http3/server.go
index df3584cc..b798abd4 100644
--- a/http3/server.go
+++ b/http3/server.go
@@ -92,8 +92,7 @@ type Server struct {
 	// See https://www.ietf.org/archive/id/draft-schinazi-masque-h3-datagram-02.html.
 	EnableDatagrams bool
 
-	port             uint32 // used atomically
-	customAltSvcPort uint32 // custom port used for Alt-Svc response header
+	port uint32 // used atomically
 
 	mutex     sync.Mutex
 	listeners map[*quic.EarlyListener]struct{}
@@ -440,22 +439,16 @@ func (s *Server) SetQuicHeaders(hdr http.Header) error {
 	port := atomic.LoadUint32(&s.port)
 
 	if port == 0 {
-		if s.customAltSvcPort != 0 {
-			// Use customAltSvcPort if set
-			port = s.customAltSvcPort
-		} else {
-			// Extract port from s.Server.Addr
-			_, portStr, err := net.SplitHostPort(s.Server.Addr)
-			if err != nil {
-				return err
-			}
-			portInt, err := net.LookupPort("tcp", portStr)
-			if err != nil {
-				return err
-			}
-			port = uint32(portInt)
+		// Extract port from s.Server.Addr
+		_, portStr, err := net.SplitHostPort(s.Server.Addr)
+		if err != nil {
+			return err
 		}
-
+		portInt, err := net.LookupPort("tcp", portStr)
+		if err != nil {
+			return err
+		}
+		port = uint32(portInt)
 		atomic.StoreUint32(&s.port, port)
 	}
 
@@ -493,17 +486,6 @@ func ListenAndServeQUIC(addr, certFile, keyFile string, handler http.Handler) er
 // http.DefaultServeMux is used when handler is nil.
 // The correct Alt-Svc headers for QUIC are set.
 func ListenAndServe(addr, certFile, keyFile string, handler http.Handler) error {
-	return ListenAndServeWithCustomAltSvcPort(addr, certFile, keyFile, handler, 0)
-}
-
-// ListenAndServeWithCustomAltSvcPort listens on the given network address for both, TLS and QUIC
-// connetions in parallel. It returns if one of the two returns an error.
-// http.DefaultServeMux is used when handler is nil.
-// The correct Alt-Svc headers for QUIC are set.
-// customAltSvcPort is used to override the default port value in the Alt-Svc response header.
-// This is useful when a Layer 4 firewall is redirecting UDP traffic and clients must use
-// a port different from the port the QUIC server itself is listening on.
-func ListenAndServeWithCustomAltSvcPort(addr, certFile, keyFile string, handler http.Handler, customAltSvcPort uint32) error {
 	// Load certs
 	var err error
 	certs := make([]tls.Certificate, 1)
@@ -548,8 +530,7 @@ func ListenAndServeWithCustomAltSvcPort(addr, certFile, keyFile string, handler
 	}
 
 	quicServer := &Server{
-		Server:           httpServer,
-		customAltSvcPort: customAltSvcPort,
+		Server: httpServer,
 	}
 
 	if handler == nil {