diff --git a/internal/net/udp/packet_conn.go b/internal/net/udp/packet_conn.go
index a39119aac..430c946fc 100644
--- a/internal/net/udp/packet_conn.go
+++ b/internal/net/udp/packet_conn.go
@@ -269,7 +269,7 @@ type PacketConn struct {
 
 	raddr   net.Addr
 	rmraddr atomic.Value // bool
-	id      atomic.Value
+	id      atomic.Value // string
 
 	buffer *idtlsnet.PacketBuffer