diff --git a/src/gap.h b/src/gap.h
index 960c3f3d6..3432c52ce 100644
--- a/src/gap.h
+++ b/src/gap.h
@@ -243,6 +243,9 @@ typedef struct {
     const le_audio_big_params_t * params;
     // request to send
     bool can_send_now_requested;
+    // previous and current timestamp of number completed event to track ISO intervals
+    bool     num_completed_timestamp_current_valid;
+    uint32_t num_completed_timestamp_current_ms;
 } le_audio_big_t;
 
 typedef struct {
diff --git a/src/hci.c b/src/hci.c
index f6504e4c4..dae8d1c7e 100644
--- a/src/hci.c
+++ b/src/hci.c
@@ -3255,6 +3255,14 @@ static void event_handler(uint8_t *packet, uint16_t size){
                             log_error("hci_number_completed_packets, more packet slots freed then sent.");
                             iso_stream->num_packets_sent = 0;
                         }
+                        uint8_t big_handle = iso_stream->big_handle;
+                        if (big_handle != 0xff){
+                            le_audio_big_t * big = hci_big_for_handle(big_handle);
+                            if (big != NULL){
+                                big->num_completed_timestamp_current_valid = true;
+                                big->num_completed_timestamp_current_ms = btstack_run_loop_get_time_ms();
+                            }
+                        }
                         log_info("hci_number_completed_packet %u processed for handle %u, outstanding %u",
                                  num_packets, handle, iso_stream->num_packets_sent);
                         notify_iso = true;