diff --git a/simplehlfhr/simple.go b/simplehlfhr/simple.go
index 9d13817..b275f87 100644
--- a/simplehlfhr/simple.go
+++ b/simplehlfhr/simple.go
@@ -48,20 +48,21 @@ func ListenAndServeTLS(srv *http.Server, certFile, keyFile string) error {
 }
 
 func NewListener(inner net.Listener, srv *http.Server) net.Listener {
-	l, ok := inner.(*Listener)
-	if !ok {
-		l = &Listener{Listener: inner}
+	if _, ok := inner.(isMyListener); ok {
+		return inner
+	}
+	return &listener{
+		Listener: inner,
+		srv:      srv,
 	}
-	l.HttpServer = srv
-	return l
 }
 
-type Listener struct {
+type listener struct {
 	net.Listener
-	HttpServer *http.Server
+	srv *http.Server
 }
 
-func (l *Listener) Accept() (c net.Conn, err error) {
+func (l *listener) Accept() (c net.Conn, err error) {
 	c, err = l.Listener.Accept()
 	if err == nil {
 		c = &conn{
@@ -72,15 +73,21 @@ func (l *Listener) Accept() (c net.Conn, err error) {
 	return
 }
 
+type isMyListener interface {
+	IsHttpsListenerForHttpRedirect()
+}
+
+func (l *listener) IsHttpsListenerForHttpRedirect() {}
+
 type conn struct {
 	net.Conn
 	// Reading TLS if nil
-	l *Listener
+	l *listener
 }
 
 func (c *conn) maxHeaderLen() int {
-	if c.l.HttpServer != nil && c.l.HttpServer.MaxHeaderBytes != 0 {
-		return c.l.HttpServer.MaxHeaderBytes
+	if c.l.srv != nil && c.l.srv.MaxHeaderBytes != 0 {
+		return c.l.srv.MaxHeaderBytes
 	}
 	return http.DefaultMaxHeaderBytes
 }
diff --git a/src_conn.go b/src_conn.go
index bf14aaf..93e5688 100644
--- a/src_conn.go
+++ b/src_conn.go
@@ -12,12 +12,12 @@ var ErrHttpOnHttpsPort = errors.New("client sent an HTTP request to an HTTPS ser
 type conn struct {
 	net.Conn
 	// Reading TLS if nil
-	l *Listener
+	l *listener
 }
 
 func (c *conn) log(v ...any) {
-	if c.l.HttpServer != nil && c.l.HttpServer.ErrorLog != nil {
-		c.l.HttpServer.ErrorLog.Print(v...)
+	if c.l.srv != nil && c.l.srv.ErrorLog != nil {
+		c.l.srv.ErrorLog.Print(v...)
 	} else {
 		log.Print(v...)
 	}
@@ -25,7 +25,7 @@ func (c *conn) log(v ...any) {
 
 func (c *conn) readRequest(b []byte, n int) (req *http.Request, errStr string) {
 	rd := &MaxHeaderBytesReader{Rd: c.Conn}
-	rd.SetMax(c.l.HttpServer)
+	rd.SetMax(c.l.srv)
 	rd.Max -= n
 
 	br := NewBufioReaderWithBytes(b, n, rd)
@@ -68,9 +68,9 @@ func (c *conn) Read(b []byte) (int, error) {
 
 	// Response
 	w := newResponse()
-	if c.l.HttpOnHttpsPortErrorHandler != nil {
+	if c.l.handler != nil {
 		// Handler
-		c.l.HttpOnHttpsPortErrorHandler.ServeHTTP(w, r)
+		c.l.handler.ServeHTTP(w, r)
 	} else {
 		// Redirect
 		RedirectToHttps(w, r, 302)
diff --git a/src_listener.go b/src_listener.go
index 37dc54a..b4868ef 100644
--- a/src_listener.go
+++ b/src_listener.go
@@ -5,28 +5,28 @@ import (
 	"net/http"
 )
 
-type Listener struct {
+type listener struct {
 	net.Listener
-
-	HttpServer                  *http.Server
-	HttpOnHttpsPortErrorHandler http.Handler
+	srv     *http.Server
+	handler http.Handler
 }
 
 func NewListener(
 	inner net.Listener,
-	httpServer *http.Server,
+	srv *http.Server,
 	httpOnHttpsPortErrorHandler http.Handler,
 ) net.Listener {
-	l, ok := inner.(*Listener)
-	if !ok {
-		l = &Listener{Listener: inner}
+	if _, ok := inner.(isMyListener); ok {
+		return inner
+	}
+	return &listener{
+		Listener: inner,
+		srv:      srv,
+		handler:  httpOnHttpsPortErrorHandler,
 	}
-	l.HttpServer = httpServer
-	l.HttpOnHttpsPortErrorHandler = httpOnHttpsPortErrorHandler
-	return l
 }
 
-func (l *Listener) Accept() (c net.Conn, err error) {
+func (l *listener) Accept() (c net.Conn, err error) {
 	c, err = l.Listener.Accept()
 	if err == nil {
 		// Hijacking net.Conn
@@ -37,3 +37,9 @@ func (l *Listener) Accept() (c net.Conn, err error) {
 	}
 	return
 }
+
+type isMyListener interface {
+	IsHttpsListenerForHttpRedirect()
+}
+
+func (l *listener) IsHttpsListenerForHttpRedirect() {}