diff --git a/homeassistant/components/mqtt/vacuum/schema_state.py b/homeassistant/components/mqtt/vacuum/schema_state.py
index 1eb763c76cd..494fc60fabd 100644
--- a/homeassistant/components/mqtt/vacuum/schema_state.py
+++ b/homeassistant/components/mqtt/vacuum/schema_state.py
@@ -206,8 +206,12 @@ class MqttStateVacuum(MqttEntity, StateVacuumEntity):
         def state_message_received(msg):
             """Handle state MQTT message."""
             payload = json.loads(msg.payload)
-            if STATE in payload and payload[STATE] in POSSIBLE_STATES:
-                self._state = POSSIBLE_STATES[payload[STATE]]
+            if STATE in payload and (
+                payload[STATE] in POSSIBLE_STATES or payload[STATE] is None
+            ):
+                self._state = (
+                    POSSIBLE_STATES[payload[STATE]] if payload[STATE] else None
+                )
                 del payload[STATE]
             self._state_attrs.update(payload)
             self.async_write_ha_state()
diff --git a/tests/components/mqtt/test_state_vacuum.py b/tests/components/mqtt/test_state_vacuum.py
index 5011f279470..a1b90f52c37 100644
--- a/tests/components/mqtt/test_state_vacuum.py
+++ b/tests/components/mqtt/test_state_vacuum.py
@@ -235,6 +235,8 @@ async def test_status(hass, mqtt_mock):
 
     assert await async_setup_component(hass, vacuum.DOMAIN, {vacuum.DOMAIN: config})
     await hass.async_block_till_done()
+    state = hass.states.get("vacuum.mqtttest")
+    assert state.state == STATE_UNKNOWN
 
     message = """{
         "battery_level": 54,
@@ -262,6 +264,11 @@ async def test_status(hass, mqtt_mock):
     assert state.attributes.get(ATTR_FAN_SPEED) == "min"
     assert state.attributes.get(ATTR_FAN_SPEED_LIST) == ["min", "medium", "high", "max"]
 
+    message = '{"state":null}'
+    async_fire_mqtt_message(hass, "vacuum/state", message)
+    state = hass.states.get("vacuum.mqtttest")
+    assert state.state == STATE_UNKNOWN
+
 
 async def test_no_fan_vacuum(hass, mqtt_mock):
     """Test status updates from the vacuum when fan is not supported."""