diff --git a/homeassistant/components/mqtt/discovery.py b/homeassistant/components/mqtt/discovery.py
index a3b120410c5..d01fb848eab 100644
--- a/homeassistant/components/mqtt/discovery.py
+++ b/homeassistant/components/mqtt/discovery.py
@@ -18,7 +18,7 @@ from homeassistant.components.mqtt import CONF_STATE_TOPIC
 _LOGGER = logging.getLogger(__name__)
 
 TOPIC_MATCHER = re.compile(
-    r'homeassistant/(?P<component>\w+)/(?P<object_id>\w+)/config')
+    r'(?P<prefix_topic>\w+)/(?P<component>\w+)/(?P<object_id>\w+)/config')
 
 SUPPORTED_COMPONENTS = ['binary_sensor', 'sensor']
 
@@ -26,6 +26,7 @@ SUPPORTED_COMPONENTS = ['binary_sensor', 'sensor']
 @asyncio.coroutine
 def async_start(hass, discovery_topic, hass_config):
     """Initialization of MQTT Discovery."""
+    # pylint: disable=unused-variable
     @asyncio.coroutine
     def async_device_message_received(topic, payload, qos):
         """Process the received message."""
@@ -34,7 +35,7 @@ def async_start(hass, discovery_topic, hass_config):
         if not match:
             return
 
-        component, object_id = match.groups()
+        prefix_topic, component, object_id = match.groups()
 
         try:
             payload = json.loads(payload)
diff --git a/tests/components/mqtt/test_discovery.py b/tests/components/mqtt/test_discovery.py
index 389fb37b489..134b679daea 100644
--- a/tests/components/mqtt/test_discovery.py
+++ b/tests/components/mqtt/test_discovery.py
@@ -1,4 +1,4 @@
-"""The tests for the MQTT component."""
+"""The tests for the MQTT discovery."""
 import asyncio
 from unittest.mock import patch
 
@@ -23,7 +23,7 @@ def test_subscribing_config_topic(hass, mqtt_mock):
 @asyncio.coroutine
 @patch('homeassistant.components.mqtt.discovery.async_load_platform')
 def test_invalid_topic(mock_load_platform, hass, mqtt_mock):
-    """Test sending in invalid JSON."""
+    """Test sending to invalid topic."""
     mock_load_platform.return_value = mock_coro()
     yield from async_start(hass, 'homeassistant', {})
 
@@ -50,7 +50,7 @@ def test_invalid_json(mock_load_platform, hass, mqtt_mock, caplog):
 @asyncio.coroutine
 @patch('homeassistant.components.mqtt.discovery.async_load_platform')
 def test_only_valid_components(mock_load_platform, hass, mqtt_mock, caplog):
-    """Test sending in invalid JSON."""
+    """Test for a valid component."""
     mock_load_platform.return_value = mock_coro()
     yield from async_start(hass, 'homeassistant', {})
 
@@ -62,7 +62,7 @@ def test_only_valid_components(mock_load_platform, hass, mqtt_mock, caplog):
 
 @asyncio.coroutine
 def test_correct_config_discovery(hass, mqtt_mock, caplog):
-    """Test sending in invalid JSON."""
+    """Test sending in correct JSON."""
     yield from async_start(hass, 'homeassistant', {})
 
     async_fire_mqtt_message(hass, 'homeassistant/binary_sensor/bla/config',