diff --git a/probe_socks5.go b/probe_socks5.go
index feef126..2adc61f 100644
--- a/probe_socks5.go
+++ b/probe_socks5.go
@@ -58,7 +58,7 @@ func (c *socks5PacketConn) ReadFrom(p []byte) (n int, addr net.Addr, err error)
 		return 0, nil, err
 	}
 	if n < 10 {
-		return 0, nil, nil
+		return 0, nil, errors.New("packet too short")
 	}
 	atyp := buf[3]
 	var rAddr *net.UDPAddr