diff --git a/source/6LoWPAN/ws/ws_llc_data_service.c b/source/6LoWPAN/ws/ws_llc_data_service.c
index f2b59af5055..53b2a9e9e93 100644
--- a/source/6LoWPAN/ws/ws_llc_data_service.c
+++ b/source/6LoWPAN/ws/ws_llc_data_service.c
@@ -635,7 +635,7 @@ static uint16_t ws_mpx_header_size_get(llc_data_base_t *base, uint16_t user_id)
         }
 
         //Dynamic length
-        header_size += 2 + WS_WP_SUB_IE_ELEMENT_HEADER_LENGTH + ws_wp_nested_hopping_schedule_length(base->ie_params.hopping_schedule, true);
+        header_size += 2 + WS_WP_SUB_IE_ELEMENT_HEADER_LENGTH + ws_wp_nested_hopping_schedule_length(base->ie_params.hopping_schedule, true) + ws_wp_nested_hopping_schedule_length(base->ie_params.hopping_schedule, false);
 
     } else if (MPX_KEY_MANAGEMENT_ENC_USER_ID) {
         header_size += 7 + 5 + 2;
@@ -704,6 +704,11 @@ static void ws_llc_mpx_data_request(const mpx_api_t *api, const struct mcps_data
         if (base->ie_params.vendor_payload_length) {
             nested_wp_id.vp_ie = true;
         }
+
+        if (!data->TxAckReq) {
+            nested_wp_id.bs_ie = true;
+        }
+
     } else if (user_id == MPX_KEY_MANAGEMENT_ENC_USER_ID) {
         ie_header_mask.bt_ie = ws_eapol_relay_state_active(base->interface_ptr);
         ie_header_mask.ea_ie = ws_eapol_handshake_first_msg(data->msdu, data->msduLength, base->interface_ptr);