diff --git a/lib/platform_esp32_idf.c b/lib/platform_esp32_idf.c
index e424db1..a84e6fb 100644
--- a/lib/platform_esp32_idf.c
+++ b/lib/platform_esp32_idf.c
@@ -22,13 +22,13 @@ static const char *TAG = "platform";
 #endif
 char *platform_create_id_string(void)
 {
-    uint8_t mac[6];
     char *id_string = calloc(1, MAX_ID_STRING);
     ESP_MEM_CHECK(TAG, id_string, return NULL);
     #ifndef MAC_TYPE
     ESP_LOGW(TAG, "Soc doesn't provide MAC, client could be disconnected in case of device with same name in the broker.");
     sprintf(id_string, "esp_mqtt_client_id");
     #else
+    uint8_t mac[6];
     esp_read_mac(mac, MAC_TYPE);
     sprintf(id_string, "ESP32_%02x%02X%02X", mac[3], mac[4], mac[5]);
     #endif