diff --git a/homeassistant/components/mold_indicator/config_flow.py b/homeassistant/components/mold_indicator/config_flow.py
index fc5c5ee953b1ae..8f2c212ade0f65 100644
--- a/homeassistant/components/mold_indicator/config_flow.py
+++ b/homeassistant/components/mold_indicator/config_flow.py
@@ -162,6 +162,7 @@ def async_preview_updated(state: str, attributes: Mapping[str, Any]) -> None:
         outdoor_temp,
         indoor_hum,
         msg["user_input"].get(CONF_CALIBRATION_FACTOR),
+        None,
     )
     preview_entity.hass = hass
 
diff --git a/homeassistant/components/mold_indicator/sensor.py b/homeassistant/components/mold_indicator/sensor.py
index 6aaee817016857..de949ab72d845f 100644
--- a/homeassistant/components/mold_indicator/sensor.py
+++ b/homeassistant/components/mold_indicator/sensor.py
@@ -91,6 +91,7 @@ async def async_setup_platform(
                 outdoor_temp_sensor,
                 indoor_humidity_sensor,
                 calib_factor,
+                None,
             )
         ],
         False,
@@ -119,6 +120,7 @@ async def async_setup_entry(
                 outdoor_temp_sensor,
                 indoor_humidity_sensor,
                 calib_factor,
+                entry.entry_id,
             )
         ],
         False,
@@ -142,10 +144,12 @@ def __init__(
         outdoor_temp_sensor: str,
         indoor_humidity_sensor: str,
         calib_factor: float,
+        unique_id: str | None,
     ) -> None:
         """Initialize the sensor."""
         self._state: str | None = None
         self._attr_name = name
+        self._attr_unique_id = unique_id
         self._indoor_temp_sensor = indoor_temp_sensor
         self._indoor_humidity_sensor = indoor_humidity_sensor
         self._outdoor_temp_sensor = outdoor_temp_sensor