diff --git a/homeassistant/components/mqtt/lock.py b/homeassistant/components/mqtt/lock.py
index b9c095a054a..235eacc9454 100644
--- a/homeassistant/components/mqtt/lock.py
+++ b/homeassistant/components/mqtt/lock.py
@@ -79,12 +79,14 @@ class MqttLock(MqttAttributes, MqttAvailability, MqttDiscoveryUpdate,
 
     def __init__(self, config, config_entry, discovery_hash):
         """Initialize the lock."""
-        self._config = config
         self._unique_id = config.get(CONF_UNIQUE_ID)
         self._state = False
         self._sub_state = None
         self._optimistic = False
 
+        # Load config
+        self._setup_from_config(config)
+
         device_config = config.get(CONF_DEVICE)
 
         MqttAttributes.__init__(self, config)
@@ -101,13 +103,19 @@ class MqttLock(MqttAttributes, MqttAvailability, MqttDiscoveryUpdate,
     async def discovery_update(self, discovery_payload):
         """Handle updated discovery message."""
         config = PLATFORM_SCHEMA(discovery_payload)
-        self._config = config
+        self._setup_from_config(config)
         await self.attributes_discovery_update(config)
         await self.availability_discovery_update(config)
         await self.device_info_discovery_update(config)
         await self._subscribe_topics()
         self.async_write_ha_state()
 
+    def _setup_from_config(self, config):
+        """(Re)Setup the entity."""
+        self._config = config
+
+        self._optimistic = config[CONF_OPTIMISTIC]
+
     async def _subscribe_topics(self):
         """(Re)Subscribe to topics."""
         value_template = self._config.get(CONF_VALUE_TEMPLATE)
diff --git a/tests/components/lock/common.py b/tests/components/lock/common.py
index 2150b3cb894..c5a71a3eb96 100644
--- a/tests/components/lock/common.py
+++ b/tests/components/lock/common.py
@@ -6,6 +6,7 @@ components. Instead call the service directly.
 from homeassistant.components.lock import DOMAIN
 from homeassistant.const import (
     ATTR_CODE, ATTR_ENTITY_ID, SERVICE_LOCK, SERVICE_UNLOCK, SERVICE_OPEN)
+from homeassistant.core import callback
 from homeassistant.loader import bind_hass
 
 
@@ -21,6 +22,19 @@ def lock(hass, entity_id=None, code=None):
     hass.services.call(DOMAIN, SERVICE_LOCK, data)
 
 
+@callback
+@bind_hass
+def async_lock(hass, entity_id=None, code=None):
+    """Lock all or specified locks."""
+    data = {}
+    if code:
+        data[ATTR_CODE] = code
+    if entity_id:
+        data[ATTR_ENTITY_ID] = entity_id
+
+    hass.async_add_job(hass.services.async_call(DOMAIN, SERVICE_LOCK, data))
+
+
 @bind_hass
 def unlock(hass, entity_id=None, code=None):
     """Unlock all or specified locks."""
@@ -33,6 +47,19 @@ def unlock(hass, entity_id=None, code=None):
     hass.services.call(DOMAIN, SERVICE_UNLOCK, data)
 
 
+@callback
+@bind_hass
+def async_unlock(hass, entity_id=None, code=None):
+    """Lock all or specified locks."""
+    data = {}
+    if code:
+        data[ATTR_CODE] = code
+    if entity_id:
+        data[ATTR_ENTITY_ID] = entity_id
+
+    hass.async_add_job(hass.services.async_call(DOMAIN, SERVICE_UNLOCK, data))
+
+
 @bind_hass
 def open_lock(hass, entity_id=None, code=None):
     """Open all or specified locks."""
@@ -43,3 +70,16 @@ def open_lock(hass, entity_id=None, code=None):
         data[ATTR_ENTITY_ID] = entity_id
 
     hass.services.call(DOMAIN, SERVICE_OPEN, data)
+
+
+@callback
+@bind_hass
+def async_open_lock(hass, entity_id=None, code=None):
+    """Lock all or specified locks."""
+    data = {}
+    if code:
+        data[ATTR_CODE] = code
+    if entity_id:
+        data[ATTR_ENTITY_ID] = entity_id
+
+    hass.async_add_job(hass.services.async_call(DOMAIN, SERVICE_OPEN, data))
diff --git a/tests/components/mqtt/test_lock.py b/tests/components/mqtt/test_lock.py
index 52dd3ecfbdb..cc629b2165d 100644
--- a/tests/components/mqtt/test_lock.py
+++ b/tests/components/mqtt/test_lock.py
@@ -11,6 +11,7 @@ from homeassistant.setup import async_setup_component
 from tests.common import (
     MockConfigEntry, async_fire_mqtt_message, async_mock_mqtt_component,
     mock_registry)
+from tests.components.lock import common
 
 
 async def test_controlling_state_via_topic(hass, mqtt_mock):
@@ -75,6 +76,82 @@ async def test_controlling_state_via_topic_and_json_message(hass, mqtt_mock):
     assert state.state is STATE_UNLOCKED
 
 
+async def test_sending_mqtt_commands_and_optimistic(hass, mqtt_mock):
+    """Test optimistic mode without state topic."""
+    assert await async_setup_component(hass, lock.DOMAIN, {
+        lock.DOMAIN: {
+            'platform': 'mqtt',
+            'name': 'test',
+            'command_topic': 'command-topic',
+            'payload_lock': 'LOCK',
+            'payload_unlock': 'UNLOCK'
+        }
+    })
+
+    state = hass.states.get('lock.test')
+    assert state.state is STATE_UNLOCKED
+    assert state.attributes.get(ATTR_ASSUMED_STATE)
+
+    common.async_lock(hass, 'lock.test')
+    await hass.async_block_till_done()
+
+    mqtt_mock.async_publish.assert_called_once_with(
+        'command-topic', 'LOCK', 0, False)
+    mqtt_mock.async_publish.reset_mock()
+    state = hass.states.get('lock.test')
+    assert state.state is STATE_LOCKED
+    assert state.attributes.get(ATTR_ASSUMED_STATE)
+
+    common.async_unlock(hass, 'lock.test')
+    await hass.async_block_till_done()
+
+    mqtt_mock.async_publish.assert_called_once_with(
+        'command-topic', 'UNLOCK', 0, False)
+    mqtt_mock.async_publish.reset_mock()
+    state = hass.states.get('lock.test')
+    assert state.state is STATE_UNLOCKED
+    assert state.attributes.get(ATTR_ASSUMED_STATE)
+
+
+async def test_sending_mqtt_commands_and_explicit_optimistic(hass, mqtt_mock):
+    """Test optimistic mode without state topic."""
+    assert await async_setup_component(hass, lock.DOMAIN, {
+        lock.DOMAIN: {
+            'platform': 'mqtt',
+            'name': 'test',
+            'state_topic': 'state-topic',
+            'command_topic': 'command-topic',
+            'payload_lock': 'LOCK',
+            'payload_unlock': 'UNLOCK',
+            'optimistic': True
+        }
+    })
+
+    state = hass.states.get('lock.test')
+    assert state.state is STATE_UNLOCKED
+    assert state.attributes.get(ATTR_ASSUMED_STATE)
+
+    common.async_lock(hass, 'lock.test')
+    await hass.async_block_till_done()
+
+    mqtt_mock.async_publish.assert_called_once_with(
+        'command-topic', 'LOCK', 0, False)
+    mqtt_mock.async_publish.reset_mock()
+    state = hass.states.get('lock.test')
+    assert state.state is STATE_LOCKED
+    assert state.attributes.get(ATTR_ASSUMED_STATE)
+
+    common.async_unlock(hass, 'lock.test')
+    await hass.async_block_till_done()
+
+    mqtt_mock.async_publish.assert_called_once_with(
+        'command-topic', 'UNLOCK', 0, False)
+    mqtt_mock.async_publish.reset_mock()
+    state = hass.states.get('lock.test')
+    assert state.state is STATE_UNLOCKED
+    assert state.attributes.get(ATTR_ASSUMED_STATE)
+
+
 async def test_default_availability_payload(hass, mqtt_mock):
     """Test availability by default payload with defined topic."""
     assert await async_setup_component(hass, lock.DOMAIN, {