diff --git a/homeassistant/components/rainmachine/sensor.py b/homeassistant/components/rainmachine/sensor.py
index 5a5329ad1fa..e57386fe0ec 100644
--- a/homeassistant/components/rainmachine/sensor.py
+++ b/homeassistant/components/rainmachine/sensor.py
@@ -243,10 +243,8 @@ class TimeRemainingSensor(RainMachineEntity, RestoreSensor):
             seconds_remaining = self.calculate_seconds_remaining()
             new_timestamp = now + timedelta(seconds=seconds_remaining)
 
-            assert isinstance(self._attr_native_value, datetime)
-
             if (
-                self._attr_native_value
+                isinstance(self._attr_native_value, datetime)
                 and new_timestamp - self._attr_native_value
                 < DEFAULT_ZONE_COMPLETION_TIME_WOBBLE_TOLERANCE
             ):