diff --git a/sonoff/_releasenotes.ino b/sonoff/_releasenotes.ino
index 5433509f8..02b23f821 100644
--- a/sonoff/_releasenotes.ino
+++ b/sonoff/_releasenotes.ino
@@ -1,8 +1,8 @@
 /* 5.11.1e
  * Replaced command Ina219Mode with command Sensor13
- * Add command Sensor15 2 to start MHZ19(B) Zero Point Calibration
  * Add chunked webserver pages for large pages saving memory
  * Fix Non-English JSON temperature unit attachement
+ * Add command Sensor15 2 to start MHZ19(B) Zero Point Calibration (#1643)
  * Fix Sonoff Pow Energy Today and Energy Total reading after restart (#1648)
  * Rewrite function pointers to save code space and memory (#1683)
  * Add option define HOME_ASSISTANT_DISCOVERY_ENABLE in user_config.h (#1685)
diff --git a/sonoff/xsns_15_mhz19.ino b/sonoff/xsns_15_mhz19.ino
index 32d37a790..79c427ca9 100644
--- a/sonoff/xsns_15_mhz19.ino
+++ b/sonoff/xsns_15_mhz19.ino
@@ -230,7 +230,7 @@ bool MhzCommandSensor()
 
   switch (XdrvMailbox.payload) {
     case 2:
-//      MhzSerial->write(mhz_cmnd_zeropoint, 9);
+      MhzSerial->write(mhz_cmnd_zeropoint, 9);
       snprintf_P(mqtt_data, sizeof(mqtt_data), S_JSON_SENSOR_INDEX_SVALUE, XSNS_15, D_JSON_ZERO_POINT_CALIBRATION);
       break;
     default: