diff --git a/homeassistant/components/number/__init__.py b/homeassistant/components/number/__init__.py
index 1ebd35711ac..3c7f7d2ca52 100644
--- a/homeassistant/components/number/__init__.py
+++ b/homeassistant/components/number/__init__.py
@@ -373,7 +373,8 @@ class NumberEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
     @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/number/const.py b/homeassistant/components/number/const.py
index 76af35adeba..ba460736455 100644
--- a/homeassistant/components/number/const.py
+++ b/homeassistant/components/number/const.py
@@ -560,7 +560,7 @@ UNIT_CONVERTERS: dict[NumberDeviceClass, type[BaseUnitConverter]] = {
 
 # We translate units that were using using the legacy coding of μ \u00b5
 # to units using recommended coding of μ \u03bc
-AMBIGUOUS_UNITS: dict[str | None, str] = {
+AMBIGUOUS_UNITS: dict[str, str] = {
     "\u00b5Sv/h": "μSv/h",  # aranet: radiation rate
     "\u00b5S/cm": UnitOfConductivity.MICROSIEMENS_PER_CM,
     "\u00b5V": UnitOfElectricPotential.MICROVOLT,
diff --git a/homeassistant/components/sensor/__init__.py b/homeassistant/components/sensor/__init__.py
index 56171707338..acc0a476219 100644
--- a/homeassistant/components/sensor/__init__.py
+++ b/homeassistant/components/sensor/__init__.py
@@ -474,7 +474,8 @@ class SensorEntity(Entity, cached_properties=CACHED_PROPERTIES_WITH_ATTR_):
     @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 e09923ad940..6550450b27b 100644
--- a/homeassistant/components/sensor/const.py
+++ b/homeassistant/components/sensor/const.py
@@ -792,7 +792,7 @@ STATE_CLASS_UNITS: dict[SensorStateClass | str, set[type[StrEnum] | str | None]]
 
 # We translate units that were using using the legacy coding of μ \u00b5
 # to units using recommended coding of μ \u03bc
-AMBIGUOUS_UNITS: dict[str | None, str] = {
+AMBIGUOUS_UNITS: dict[str, str] = {
     "\u00b5Sv/h": "μSv/h",  # aranet: radiation rate
     "\u00b5S/cm": UnitOfConductivity.MICROSIEMENS_PER_CM,
     "\u00b5V": UnitOfElectricPotential.MICROVOLT,