diff --git a/lib/include/mqtt_outbox.h b/lib/include/mqtt_outbox.h
index 8d5f342..21b1436 100644
--- a/lib/include/mqtt_outbox.h
+++ b/lib/include/mqtt_outbox.h
@@ -16,6 +16,7 @@ struct outbox_item;
 typedef struct outbox_list_t *outbox_handle_t;
 typedef struct outbox_item *outbox_item_handle_t;
 typedef struct outbox_message *outbox_message_handle_t;
+typedef long long outbox_tick_t;
 
 typedef struct outbox_message {
     uint8_t *data;
@@ -35,17 +36,17 @@ typedef enum pending_state {
 } pending_state_t;
 
 outbox_handle_t outbox_init(void);
-outbox_item_handle_t outbox_enqueue(outbox_handle_t outbox, outbox_message_handle_t message, int tick);
-outbox_item_handle_t outbox_dequeue(outbox_handle_t outbox, pending_state_t pending, int *tick);
+outbox_item_handle_t outbox_enqueue(outbox_handle_t outbox, outbox_message_handle_t message, outbox_tick_t tick);
+outbox_item_handle_t outbox_dequeue(outbox_handle_t outbox, pending_state_t pending, outbox_tick_t *tick);
 outbox_item_handle_t outbox_get(outbox_handle_t outbox, int msg_id);
 uint8_t *outbox_item_get_data(outbox_item_handle_t item,  size_t *len, uint16_t *msg_id, int *msg_type, int *qos);
 esp_err_t outbox_delete(outbox_handle_t outbox, int msg_id, int msg_type);
 esp_err_t outbox_delete_msgid(outbox_handle_t outbox, int msg_id);
 esp_err_t outbox_delete_msgtype(outbox_handle_t outbox, int msg_type);
-int outbox_delete_expired(outbox_handle_t outbox, int current_tick, int timeout);
+int outbox_delete_expired(outbox_handle_t outbox, outbox_tick_t current_tick, outbox_tick_t timeout);
 
 esp_err_t outbox_set_pending(outbox_handle_t outbox, int msg_id, pending_state_t pending);
-esp_err_t outbox_set_tick(outbox_handle_t outbox, int msg_id, int tick);
+esp_err_t outbox_set_tick(outbox_handle_t outbox, int msg_id, outbox_tick_t tick);
 int outbox_get_size(outbox_handle_t outbox);
 esp_err_t outbox_cleanup(outbox_handle_t outbox, int max_size);
 void outbox_destroy(outbox_handle_t outbox);
diff --git a/lib/mqtt_outbox.c b/lib/mqtt_outbox.c
index 5db1224..1723fb9 100644
--- a/lib/mqtt_outbox.c
+++ b/lib/mqtt_outbox.c
@@ -15,7 +15,7 @@ typedef struct outbox_item {
     int msg_id;
     int msg_type;
     int msg_qos;
-    int tick;
+    outbox_tick_t tick;
     int retry_count;
     pending_state_t pending;
     STAILQ_ENTRY(outbox_item) next;
@@ -32,7 +32,7 @@ outbox_handle_t outbox_init(void)
     return outbox;
 }
 
-outbox_item_handle_t outbox_enqueue(outbox_handle_t outbox, outbox_message_handle_t message, int tick)
+outbox_item_handle_t outbox_enqueue(outbox_handle_t outbox, outbox_message_handle_t message, outbox_tick_t tick)
 {
     outbox_item_handle_t item = calloc(1, sizeof(outbox_item_t));
     ESP_MEM_CHECK(TAG, item, return NULL);
@@ -67,7 +67,7 @@ outbox_item_handle_t outbox_get(outbox_handle_t outbox, int msg_id)
     return NULL;
 }
 
-outbox_item_handle_t outbox_dequeue(outbox_handle_t outbox, pending_state_t pending, int *tick)
+outbox_item_handle_t outbox_dequeue(outbox_handle_t outbox, pending_state_t pending, outbox_tick_t *tick)
 {
     outbox_item_handle_t item;
     STAILQ_FOREACH(item, outbox, next) {
@@ -131,7 +131,7 @@ esp_err_t outbox_set_pending(outbox_handle_t outbox, int msg_id, pending_state_t
     return ESP_FAIL;
 }
 
-esp_err_t outbox_set_tick(outbox_handle_t outbox, int msg_id, int tick)
+esp_err_t outbox_set_tick(outbox_handle_t outbox, int msg_id, outbox_tick_t tick)
 {
     outbox_item_handle_t item = outbox_get(outbox, msg_id);
     if (item) {
@@ -155,7 +155,7 @@ esp_err_t outbox_delete_msgtype(outbox_handle_t outbox, int msg_type)
     return ESP_OK;
 }
 
-int outbox_delete_expired(outbox_handle_t outbox, int current_tick, int timeout)
+int outbox_delete_expired(outbox_handle_t outbox, outbox_tick_t current_tick, outbox_tick_t timeout)
 {
     int deleted_items = 0;
     outbox_item_handle_t item, tmp;
diff --git a/mqtt_client.c b/mqtt_client.c
index d5ab1c3..c16a41a 100644
--- a/mqtt_client.c
+++ b/mqtt_client.c
@@ -34,6 +34,8 @@
     { if (key) { setfn(ssl, key, strlen(key)); } }
 #endif
 
+_Static_assert(sizeof(uint64_t) == sizeof(outbox_tick_t), "mqtt-client tick type size different from outbox tick type");
+
 static const char *TAG = "MQTT_CLIENT";
 
 #ifdef MQTT_SUPPORTED_FEATURE_EVENT_LOOP
@@ -1100,8 +1102,8 @@ static esp_err_t mqtt_resend_queued(esp_mqtt_client_handle_t client, outbox_item
 static void esp_mqtt_task(void *pv)
 {
     esp_mqtt_client_handle_t client = (esp_mqtt_client_handle_t) pv;
-    uint32_t last_retransmit = 0;
-    int32_t msg_tick = 0;
+    uint64_t last_retransmit = 0;
+    outbox_tick_t msg_tick = 0;
     client->run = true;
 
     //get transport by scheme