diff --git a/homeassistant/components/sensor/__init__.py b/homeassistant/components/sensor/__init__.py
index 4917ee4191b..346e5878898 100644
--- a/homeassistant/components/sensor/__init__.py
+++ b/homeassistant/components/sensor/__init__.py
@@ -470,10 +470,12 @@ class SensorEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
             return self.entity_description.native_unit_of_measurement
         return None
 
-    @cached_property
+    @final
+    @property
     def __native_unit_of_measurement_compat(self) -> str | None:
         """Process ambiguous units."""
-        native_unit_of_measurement = self.native_unit_of_measurement
+        if (native_unit_of_measurement := self.native_unit_of_measurement) is None:
+            return None
         return AMBIGUOUS_UNITS.get(
             native_unit_of_measurement, native_unit_of_measurement
         )
diff --git a/homeassistant/components/sensor/const.py b/homeassistant/components/sensor/const.py
index a158f777157..089fe6b37be 100644
--- a/homeassistant/components/sensor/const.py
+++ b/homeassistant/components/sensor/const.py
@@ -772,7 +772,7 @@ STATE_CLASS_UNITS: dict[SensorStateClass | str, set[type[StrEnum] | str | None]]
     SensorStateClass.MEASUREMENT_ANGLE: {DEGREE},
 }
 
-AMBIGUOUS_UNITS: dict[str | None, str | None] = {
+AMBIGUOUS_UNITS: dict[str, str] = {
     "\u00b5Sv/h": "μSv/h",  # aranet: radiation rate
     "\u00b5S/cm": UnitOfConductivity.MICROSIEMENS_PER_CM,
     "\u00b5V": UnitOfElectricPotential.MICROVOLT,