diff --git a/mongoose.c b/mongoose.c
index c8c9b8ab..36f02329 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -4812,7 +4812,7 @@ uint64_t mg_millis(void) {
 #endif
   return ((uint64_t) ts.tv_sec * 1000 + (uint64_t) ts.tv_nsec / 1000000);
 #else
-  return time(NULL) * 1000;
+  return (uint64_t) (time(NULL) * 1000);
 #endif
 }
 #endif
diff --git a/src/util.c b/src/util.c
index abaaabef..8d6a8df3 100644
--- a/src/util.c
+++ b/src/util.c
@@ -111,7 +111,7 @@ uint64_t mg_millis(void) {
 #endif
   return ((uint64_t) ts.tv_sec * 1000 + (uint64_t) ts.tv_nsec / 1000000);
 #else
-  return time(NULL) * 1000;
+  return (uint64_t) (time(NULL) * 1000);
 #endif
 }
 #endif
diff --git a/test/unit_test.c b/test/unit_test.c
index c95d6fd2..bebe812b 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -333,10 +333,25 @@ static void test_sntp(void) {
   ASSERT(mg_sntp_parse(NULL, 0) == -1);
 }
 
+struct mqtt_data {
+  char *buf;
+  int subscribed;
+  int published;
+};
+
 static void mqtt_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
-  char *buf = (char *) fnd;
+  struct mqtt_data *test_data = (struct mqtt_data *) fnd;
+  char *buf = test_data->buf;
   if (ev == MG_EV_MQTT_OPEN) {
     buf[0] = *(int *) evd == 0 ? 'X' : 'Y';
+  } else if (ev == MG_EV_MQTT_CMD) {
+    struct mg_mqtt_message *mm = (struct mg_mqtt_message *) evd;
+    if (mm->cmd == MQTT_CMD_SUBACK) {
+      test_data->subscribed = 1;
+    }
+    if (mm->cmd == MQTT_CMD_PUBACK) {
+      test_data->published = 1;
+    }
   } else if (ev == MG_EV_MQTT_MSG) {
     struct mg_mqtt_message *mm = (struct mg_mqtt_message *) evd;
     sprintf(buf + 1, "%.*s/%.*s", (int) mm->topic.len, mm->topic.ptr,
@@ -347,10 +362,12 @@ static void mqtt_cb(struct mg_connection *c, int ev, void *evd, void *fnd) {
 
 static void test_mqtt(void) {
   char buf[50] = {0};
+  struct mqtt_data test_data = {buf, 0, 0};
   struct mg_mgr mgr;
   struct mg_str topic = mg_str("x/f12"), data = mg_str("hi");
   struct mg_connection *c;
   struct mg_mqtt_opts opts;
+  char rnd[9], client_id[16];
   // const char *url = "mqtt://mqtt.eclipse.org:1883";
   const char *url = "mqtt://broker.hivemq.com:1883";
   int i;
@@ -363,32 +380,49 @@ static void test_mqtt(void) {
   }
 
   // Connect with empty client ID
-  c = mg_mqtt_connect(&mgr, url, NULL, mqtt_cb, buf);
-  for (i = 0; i < 200 && buf[0] == 0; i++) mg_mgr_poll(&mgr, 10);
+  c = mg_mqtt_connect(&mgr, url, NULL, mqtt_cb, &test_data);
+  for (i = 0; i < 300 && buf[0] == 0; i++) mg_mgr_poll(&mgr, 10);
   if (buf[0] != 'X') MG_INFO(("[%s]", buf));
   ASSERT(buf[0] == 'X');
+  ASSERT(test_data.subscribed == 0);
   mg_mqtt_sub(c, topic, 1);
+  for (i = 0; i < 500 && test_data.subscribed == 0; i++) mg_mgr_poll(&mgr, 10);
+  ASSERT(test_data.subscribed == 1);
+  ASSERT(test_data.published == 0);
   mg_mqtt_pub(c, topic, data, 1, false);
-  for (i = 0; i < 300 && buf[1] == 0; i++) mg_mgr_poll(&mgr, 10);
+  for (i = 0; i < 500 && test_data.published == 0; i++) mg_mgr_poll(&mgr, 10);
+  ASSERT(test_data.published == 1);
+  for (i = 0; i < 500 && buf[1] == 0; i++) mg_mgr_poll(&mgr, 10);
   if (strcmp(buf, "Xx/f12/hi") != 0) MG_INFO(("[%s]", buf));
   ASSERT(strcmp(buf, "Xx/f12/hi") == 0);
 
   // Set params
+  test_data.subscribed = 0;
+  test_data.published = 0;
   memset(buf, 0, sizeof(buf));
   memset(&opts, 0, sizeof(opts));
   opts.clean = true;
   opts.will_qos = 1;
   opts.will_retain = true;
   opts.keepalive = 20;
-  opts.client_id = mg_str("mg_client");
+  mg_random(rnd, sizeof(rnd));
+  mg_base64_encode((unsigned char *) rnd, sizeof(rnd), client_id);
+  client_id[sizeof(client_id) - 1] = '\0';
+  opts.client_id = mg_str(client_id);
   opts.will_topic = mg_str("mg_will_topic");
   opts.will_message = mg_str("mg_will_messsage");
-  c = mg_mqtt_connect(&mgr, url, &opts, mqtt_cb, buf);
+  c = mg_mqtt_connect(&mgr, url, &opts, mqtt_cb, &test_data);
   for (i = 0; i < 300 && buf[0] == 0; i++) mg_mgr_poll(&mgr, 10);
   if (buf[0] != 'X') MG_INFO(("[%s]", buf));
   ASSERT(buf[0] == 'X');
+  ASSERT(test_data.subscribed == 0);
   mg_mqtt_sub(c, topic, 1);
+  for (i = 0; i < 500 && test_data.subscribed == 0; i++) mg_mgr_poll(&mgr, 10);
+  ASSERT(test_data.subscribed == 1);
+  ASSERT(test_data.published == 0);
   mg_mqtt_pub(c, topic, data, 1, false);
+  for (i = 0; i < 500 && test_data.published == 0; i++) mg_mgr_poll(&mgr, 10);
+  ASSERT(test_data.published == 1);
   for (i = 0; i < 500 && buf[1] == 0; i++) mg_mgr_poll(&mgr, 10);
   if (strcmp(buf, "Xx/f12/hi") != 0) MG_INFO(("[%s]", buf));
   ASSERT(strcmp(buf, "Xx/f12/hi") == 0);