diff --git a/homeassistant/components/lock/mqtt.py b/homeassistant/components/lock/mqtt.py
index ad5ba34dbb0..5574c7e4e59 100644
--- a/homeassistant/components/lock/mqtt.py
+++ b/homeassistant/components/lock/mqtt.py
@@ -18,7 +18,8 @@ from homeassistant.components.mqtt import (
 from homeassistant.const import (
     CONF_DEVICE, CONF_NAME, CONF_OPTIMISTIC, CONF_VALUE_TEMPLATE)
 from homeassistant.components import mqtt, lock
-from homeassistant.components.mqtt.discovery import MQTT_DISCOVERY_NEW
+from homeassistant.components.mqtt.discovery import (
+    MQTT_DISCOVERY_NEW, clear_discovery_hash)
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.dispatcher import async_dispatcher_connect
 from homeassistant.helpers.typing import HomeAssistantType, ConfigType
@@ -57,9 +58,15 @@ async def async_setup_entry(hass, config_entry, async_add_entities):
     """Set up MQTT lock dynamically through MQTT discovery."""
     async def async_discover(discovery_payload):
         """Discover and add an MQTT lock."""
-        config = PLATFORM_SCHEMA(discovery_payload)
-        await _async_setup_entity(hass, config, async_add_entities,
-                                  discovery_payload[ATTR_DISCOVERY_HASH])
+        try:
+            discovery_hash = discovery_payload[ATTR_DISCOVERY_HASH]
+            config = PLATFORM_SCHEMA(discovery_payload)
+            await _async_setup_entity(hass, config, async_add_entities,
+                                      discovery_hash)
+        except Exception:
+            if discovery_hash:
+                clear_discovery_hash(hass, discovery_hash)
+            raise
 
     async_dispatcher_connect(
         hass, MQTT_DISCOVERY_NEW.format(lock.DOMAIN, 'mqtt'),
diff --git a/tests/components/lock/test_mqtt.py b/tests/components/lock/test_mqtt.py
index 0fcb97f1b68..f3b7c45d38a 100644
--- a/tests/components/lock/test_mqtt.py
+++ b/tests/components/lock/test_mqtt.py
@@ -182,6 +182,38 @@ async def test_discovery_removal_lock(hass, mqtt_mock, caplog):
     assert state is None
 
 
+async def test_discovery_broken(hass, mqtt_mock, caplog):
+    """Test handling of bad discovery message."""
+    entry = MockConfigEntry(domain=mqtt.DOMAIN)
+    await async_start(hass, 'homeassistant', {}, entry)
+
+    data1 = (
+        '{ "name": "Beer" }'
+    )
+    data2 = (
+        '{ "name": "Milk",'
+        '  "command_topic": "test_topic" }'
+    )
+
+    async_fire_mqtt_message(hass, 'homeassistant/lock/bla/config',
+                            data1)
+    await hass.async_block_till_done()
+
+    state = hass.states.get('lock.beer')
+    assert state is None
+
+    async_fire_mqtt_message(hass, 'homeassistant/lock/bla/config',
+                            data2)
+    await hass.async_block_till_done()
+    await hass.async_block_till_done()
+
+    state = hass.states.get('lock.milk')
+    assert state is not None
+    assert state.name == 'Milk'
+    state = hass.states.get('lock.beer')
+    assert state is None
+
+
 async def test_entity_device_info_with_identifier(hass, mqtt_mock):
     """Test MQTT lock device registry integration."""
     entry = MockConfigEntry(domain=mqtt.DOMAIN)