diff --git a/homeassistant/components/sensor/history_stats.py b/homeassistant/components/sensor/history_stats.py
index de7b7ebaf9e..7af858b9d94 100644
--- a/homeassistant/components/sensor/history_stats.py
+++ b/homeassistant/components/sensor/history_stats.py
@@ -106,8 +106,8 @@ class HistoryStatsSensor(Entity):
         self._unit_of_measurement = UNITS[sensor_type]
 
         self._period = (datetime.datetime.now(), datetime.datetime.now())
-        self.value = 0
-        self.count = 0
+        self.value = None
+        self.count = None
 
         def force_refresh(*args):
             """Force the component to refresh."""
@@ -127,6 +127,9 @@ class HistoryStatsSensor(Entity):
     @property
     def state(self):
         """Return the state of the sensor."""
+        if self.value is None or self.count is None:
+            return None
+
         if self._type == CONF_TYPE_TIME:
             return round(self.value, 2)
 
@@ -149,6 +152,9 @@ class HistoryStatsSensor(Entity):
     @property
     def device_state_attributes(self):
         """Return the state attributes of the sensor."""
+        if self.value is None:
+            return {}
+
         hsh = HistoryStatsHelper
         return {
             ATTR_VALUE: hsh.pretty_duration(self.value),
diff --git a/tests/components/sensor/test_history_stats.py b/tests/components/sensor/test_history_stats.py
index 7fdf732825b..1a2ec086e77 100644
--- a/tests/components/sensor/test_history_stats.py
+++ b/tests/components/sensor/test_history_stats.py
@@ -4,6 +4,7 @@ from datetime import timedelta
 import unittest
 from unittest.mock import patch
 
+from homeassistant.const import STATE_UNKNOWN
 from homeassistant.setup import setup_component
 from homeassistant.components.sensor.history_stats import HistoryStatsSensor
 import homeassistant.core as ha
@@ -43,8 +44,8 @@ class TestHistoryStatsSensor(unittest.TestCase):
 
         self.assertTrue(setup_component(self.hass, 'sensor', config))
 
-        state = self.hass.states.get('sensor.test').as_dict()
-        self.assertEqual(state['state'], '0')
+        state = self.hass.states.get('sensor.test')
+        self.assertEqual(state.state, STATE_UNKNOWN)
 
     def test_period_parsing(self):
         """Test the conversion from templates to period."""
@@ -132,7 +133,7 @@ class TestHistoryStatsSensor(unittest.TestCase):
                 sensor4.update()
 
         self.assertEqual(sensor1.state, 0.5)
-        self.assertEqual(sensor2.state, 0)
+        self.assertEqual(sensor2.state, None)
         self.assertEqual(sensor3.state, 2)
         self.assertEqual(sensor4.state, 50)