diff --git a/u_conn.go b/u_conn.go
index 8668533..cc1f12d 100644
--- a/u_conn.go
+++ b/u_conn.go
@@ -587,14 +587,12 @@ func (uconn *UConn) MarshalClientHello() error {
 			return fmt.Errorf("sni extension missing while attempting ECH")
 		}
 
-		oldSNI := uconn.Extensions[sniExtIdex]
 		uconn.Extensions[sniExtIdex] = &SNIExtension{
 			ServerName: string(ech.config.PublicName),
 		}
 
 		uconn.computeAndUpdateOuterECHExtension(inner, ech, true)
 
-		uconn.Extensions[sniExtIdex] = oldSNI
 		uconn.echCtx = ech
 		return nil
 	}