diff --git a/homeassistant/components/homekit_controller/__init__.py b/homeassistant/components/homekit_controller/__init__.py
index f9fd0409c9c..44af8bffe26 100644
--- a/homeassistant/components/homekit_controller/__init__.py
+++ b/homeassistant/components/homekit_controller/__init__.py
@@ -1,6 +1,5 @@
 """Support for Homekit device discovery."""
 import logging
-import os
 
 from homeassistant.components.discovery import SERVICE_HOMEKIT
 from homeassistant.helpers import discovery
@@ -9,7 +8,7 @@ from homeassistant.helpers.entity import Entity
 from .config_flow import load_old_pairings
 from .connection import get_accessory_information, HKDevice
 from .const import (
-    CONTROLLER, HOMEKIT_DIR, KNOWN_DEVICES, PAIRING_FILE
+    CONTROLLER, KNOWN_DEVICES
 )
 from .const import DOMAIN   # noqa: pylint: disable=unused-import
 
diff --git a/homeassistant/loader.py b/homeassistant/loader.py
index 7f0d50f93d4..8ccbcaa33c4 100644
--- a/homeassistant/loader.py
+++ b/homeassistant/loader.py
@@ -83,7 +83,11 @@ def get_platform(hass,  # type: HomeAssistant
     """
     # If the platform has a component, we will limit the platform loading path
     # to be the same source (custom/built-in).
-    component = _load_file(hass, platform_name, LOOKUP_PATHS)
+    if domain not in ['automation', 'mqtt', 'telegram_bot']:
+        component = _load_file(hass, platform_name, LOOKUP_PATHS)
+    else:
+        # avoid load component for legacy platform
+        component = None
 
     # Until we have moved all platforms under their component/own folder, it
     # can be that the component is None.
@@ -99,6 +103,14 @@ def get_platform(hass,  # type: HomeAssistant
     if platform is not None:
         return platform
 
+    # Legacy platform check for automation: components/automation/event.py
+    if component is None and domain in ['automation', 'mqtt', 'telegram_bot']:
+        platform = _load_file(
+            hass,
+            PLATFORM_FORMAT.format(domain=platform_name, platform=domain),
+            base_paths
+        )
+
     # Legacy platform check for custom: custom_components/light/hue.py
     # Only check if the component was also in custom components.
     if component is None or base_paths[0] == PACKAGE_CUSTOM_COMPONENTS:
diff --git a/tests/helpers/test_entity_component.py b/tests/helpers/test_entity_component.py
index 163261a4b81..6da3293d597 100644
--- a/tests/helpers/test_entity_component.py
+++ b/tests/helpers/test_entity_component.py
@@ -324,7 +324,7 @@ def test_setup_dependencies_platform(hass):
     loader.set_component(hass, 'test_component2',
                          MockModule('test_component2'))
     loader.set_component(
-        hass, 'test_domain.test_component',
+        hass, 'test_component.test_domain',
         MockPlatform(dependencies=['test_component', 'test_component2']))
 
     component = EntityComponent(_LOGGER, DOMAIN, hass)
diff --git a/tests/test_config_entries.py b/tests/test_config_entries.py
index 324db971583..32532761ccf 100644
--- a/tests/test_config_entries.py
+++ b/tests/test_config_entries.py
@@ -192,7 +192,7 @@ async def test_remove_entry(hass, manager):
         async_remove_entry=mock_remove_entry
     ))
     loader.set_component(
-        hass, 'light.test',
+        hass, 'test.light',
         MockPlatform(async_setup_entry=mock_setup_entry_platform))
 
     MockConfigEntry(domain='test', entry_id='test1').add_to_manager(manager)