diff --git a/main/mqttDiscovery.cpp b/main/mqttDiscovery.cpp
index 6a249e9db7..ef07780fb9 100644
--- a/main/mqttDiscovery.cpp
+++ b/main/mqttDiscovery.cpp
@@ -127,6 +127,7 @@ static const char* const availableHASSUnits[] = {
     HASS_UNIT_UGM3,
     HASS_UNIT_OHM,
     HASS_UNIT_PERCENT,
+    HASS_UNIT_PPM,
     HASS_UNIT_DEGREE,
     HASS_UNIT_CELSIUS,
     HASS_UNIT_FAHRENHEIT,