diff --git a/infra/conf/transport_finalmask.go b/infra/conf/transport_finalmask.go
index c46016584..62abf3893 100644
--- a/infra/conf/transport_finalmask.go
+++ b/infra/conf/transport_finalmask.go
@@ -942,12 +942,19 @@ func (c *UDPHop) Build() (proto.Message, error) {
 		}
 		return nil, errors.New("invalid ip ", ip)
 	}
+	interval := c.Interval
+	if interval.From == 0 && interval.To == 0 {
+		interval.From, interval.To = 30, 30
+	}
+	if interval.From < 5 {
+		return nil, errors.New("interval must be at least 5")
+	}
 	return &udphop.Config{
 		Local:       local,
 		Remote:      remote,
 		RemoteOnce:  remoteOnce,
-		IntervalMin: int64(c.Interval.From),
-		IntervalMax: int64(c.Interval.To),
+		IntervalMin: int64(interval.From),
+		IntervalMax: int64(interval.To),
 		RemoteIPs:   remoteIPs,
 		RemotePorts: c.RemotePorts.Build().Ports(),
 	}, nil
diff --git a/transport/internet/finalmask/finalmask.go b/transport/internet/finalmask/finalmask.go
index 179f958f0..199e24496 100644
--- a/transport/internet/finalmask/finalmask.go
+++ b/transport/internet/finalmask/finalmask.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"slices"
 
+	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/net"
@@ -88,7 +89,7 @@ func (fm *FinalMask) DialTCP(ctx context.Context, dest net.Destination) (net.Con
 		var newConn net.Conn
 		newConn, err = fm.tcpMasks[i].WrapConnClient(conn, &dest, dialer)
 		if err != nil {
-			_ = conn.Close()
+			common.CloseIfExists(conn)
 			return nil, err
 		}
 		conn = newConn
@@ -193,7 +194,7 @@ func (fm *FinalMask) DialUDP(ctx context.Context, dest net.Destination) (net.Con
 			}
 			newConn, err = fm.udpMasks[i].WrapPacketConnClient(conn, &dest, dialer)
 			if err != nil {
-				_ = conn.Close()
+				common.CloseIfExists(conn)
 				return nil, err
 			}
 			conn = newConn
@@ -240,7 +241,7 @@ func (fm *FinalMask) ListenPacket(ctx context.Context, addr net.Addr) (net.Packe
 		if _, ok := fm.udpMasks[i].(interface{ HeaderConn() }); ok {
 			newConn, err = fm.udpMasks[i].WrapPacketConnServer(nil, nil, nil)
 			if err != nil {
-				_ = conn.Close()
+				common.CloseIfExists(conn)
 				return nil, err
 			}
 			sizes = append(sizes, newConn.(interface{ Size() int }).Size())
@@ -253,7 +254,7 @@ func (fm *FinalMask) ListenPacket(ctx context.Context, addr net.Addr) (net.Packe
 			}
 			newConn, err = fm.udpMasks[i].WrapPacketConnServer(conn, addr, lc)
 			if err != nil {
-				_ = conn.Close()
+				common.CloseIfExists(conn)
 				return nil, err
 			}
 			conn = newConn