diff --git a/fw_esp8266.ino b/fw_esp8266.ino
index 27602b0..5b9a2e9 100644
--- a/fw_esp8266.ino
+++ b/fw_esp8266.ino
@@ -2,6 +2,8 @@
  *   ESP-01 firmware, built with IotWebConf: an ESP8266/ESP32
  *   non blocking WiFi/AP web configuration library for Arduino.
  *   https://github.com/prampec/IotWebConf 
+ *   Requires a custom version of the NTPClient library, available from:
+ *   https://git.dotya.ml/2EEEB/NTPClient
  */
 
 #include <MQTT.h>