diff --git a/src/algo_lightning.c b/src/algo_lightning.c
index addd16d..b605787 100644
--- a/src/algo_lightning.c
+++ b/src/algo_lightning.c
@@ -390,7 +390,7 @@ void tag_packet_measlat(union abstract_packet* ap, uint8_t link_id, uint8_t is_s
       continue;
     }
     struct measure_packet *mp = (void*)&cur->fmt.content.udp_encapsulated.payload;
-    mp->flag = 0x7f & link_id;
+    mp->flag = 0x3f & link_id;
     mp->flag |= vanilla << 6;
     mp->flag |= is_slow << 7;