diff --git a/homeassistant/components/isy994/climate.py b/homeassistant/components/isy994/climate.py
index 1276207f23c..d68395f14da 100644
--- a/homeassistant/components/isy994/climate.py
+++ b/homeassistant/components/isy994/climate.py
@@ -6,6 +6,7 @@ from typing import Any
 from pyisy.constants import (
     CMD_CLIMATE_FAN_SETTING,
     CMD_CLIMATE_MODE,
+    ISY_VALUE_UNKNOWN,
     PROP_HEAT_COOL_STATE,
     PROP_HUMIDITY,
     PROP_SETPOINT_COOL,
@@ -116,6 +117,8 @@ class ISYThermostatEntity(ISYNodeEntity, ClimateEntity):
         """Return the current humidity."""
         if not (humidity := self._node.aux_properties.get(PROP_HUMIDITY)):
             return None
+        if humidity == ISY_VALUE_UNKNOWN:
+            return None
         return int(humidity.value)
 
     @property