diff --git a/backend/main.go b/backend/main.go
index bf80ff3..aabcf1e 100644
--- a/backend/main.go
+++ b/backend/main.go
@@ -9,6 +9,7 @@ import (
 	"encoding/pem"
 	"fmt"
 	"log"
+	"crypto/tls"
 	"math/big"
 	"net"
 	"net/http"
@@ -96,7 +97,13 @@ func main() {
 	log.Printf("RMM Backend startet auf %s (TLS)", cfg.ListenAddr)
 	log.Printf("API-Keys (Config): %d, DB-basierte Validierung aktiv", len(cfg.APIKeys))
 
-	if err := http.ListenAndServeTLS(cfg.ListenAddr, cfg.TLSCert, cfg.TLSKey, chain); err != nil {
+	// HTTP/2 deaktivieren: WebSocket-Upgrades benoetigen HTTP/1.1
+	srv := &http.Server{
+		Addr:      cfg.ListenAddr,
+		Handler:   chain,
+		TLSNextProto: make(map[string]func(*http.Server, *tls.Conn, http.Handler)),
+	}
+	if err := srv.ListenAndServeTLS(cfg.TLSCert, cfg.TLSKey); err != nil {
 		log.Fatalf("Server-Fehler: %v", err)
 	}
 }