diff --git a/CHANGELOG.md b/CHANGELOG.md
index 099d8149203..b5fac034881 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 ### Bugfix
 * Prevent sending broadcast frames on unicast channel
 * Delay sending of the first DIO message until parent selection is made and DAO target is published. Fix is made to avoid sending of DIO messages to the unstable network.
+* Accept only next possible BSI for detect BR reboot. This fix a bug when PAN timeout happen and node join correctly to new but hear old BSI after that.
 
 
 ## Release v12.6.2 (09-11-2020)
diff --git a/source/6LoWPAN/ws/ws_bootstrap.c b/source/6LoWPAN/ws/ws_bootstrap.c
index dd0f653f22d..71c623b0d1d 100644
--- a/source/6LoWPAN/ws/ws_bootstrap.c
+++ b/source/6LoWPAN/ws/ws_bootstrap.c
@@ -1624,10 +1624,15 @@ static void ws_bootstrap_pan_config_analyse(struct protocol_interface_info_entry
 
         //When Config is learned and USE Parent BS is enabled compare is this new BSI
         if (cur->ws_info->configuration_learned && cur->ws_info->pan_information.use_parent_bs && ws_bs_ie.broadcast_schedule_identifier != cur->ws_info->hopping_schdule.fhss_bsi) {
-            tr_debug("NEW Brodcast Schedule %u...BR rebooted", ws_bs_ie.broadcast_schedule_identifier);
-            cur->ws_info->ws_bsi_block.block_time = cur->ws_info->cfg->timing.pan_timeout;
-            cur->ws_info->ws_bsi_block.old_bsi = cur->ws_info->hopping_schdule.fhss_bsi;
-            ws_bootstrap_event_discovery_start(cur);
+            //Accept only next possible BSI number
+            if ((cur->ws_info->hopping_schdule.fhss_bsi + 1) != ws_bs_ie.broadcast_schedule_identifier) {
+                tr_debug("Do not accept a unknown BSI: %u", ws_bs_ie.broadcast_schedule_identifier);
+            } else {
+                tr_debug("NEW Brodcast Schedule %u...BR rebooted", ws_bs_ie.broadcast_schedule_identifier);
+                cur->ws_info->ws_bsi_block.block_time = cur->ws_info->cfg->timing.pan_timeout;
+                cur->ws_info->ws_bsi_block.old_bsi = cur->ws_info->hopping_schdule.fhss_bsi;
+                ws_bootstrap_event_discovery_start(cur);
+            }
             return;
         }
     }