diff --git a/homeassistant/components/hassio/discovery.py b/homeassistant/components/hassio/discovery.py
index ba5c8c3f789..3c5242607c1 100644
--- a/homeassistant/components/hassio/discovery.py
+++ b/homeassistant/components/hassio/discovery.py
@@ -5,7 +5,7 @@ import logging
 from aiohttp import web
 from aiohttp.web_exceptions import HTTPServiceUnavailable
 
-from homeassistant.core import callback
+from homeassistant.core import callback, CoreState
 from homeassistant.const import EVENT_HOMEASSISTANT_START
 from homeassistant.components.http import HomeAssistantView
 
@@ -40,8 +40,11 @@ def async_setup_discovery(hass, hassio, config):
         if jobs:
             await asyncio.wait(jobs)
 
-    hass.bus.async_listen_once(
-        EVENT_HOMEASSISTANT_START, async_discovery_start_handler)
+    if hass.state == CoreState.running:
+        hass.async_create_task(async_discovery_start_handler(None))
+    else:
+        hass.bus.async_listen_once(
+            EVENT_HOMEASSISTANT_START, async_discovery_start_handler)
 
     hass.http.register_view(hassio_discovery)
 
diff --git a/tests/components/hassio/conftest.py b/tests/components/hassio/conftest.py
index fb3a172a45c..f9ad1c578de 100644
--- a/tests/components/hassio/conftest.py
+++ b/tests/components/hassio/conftest.py
@@ -4,6 +4,7 @@ from unittest.mock import patch, Mock
 
 import pytest
 
+from homeassistant.core import CoreState
 from homeassistant.setup import async_setup_component
 from homeassistant.components.hassio.handler import HassIO, HassioAPIError
 
@@ -33,6 +34,7 @@ def hassio_client(hassio_env, hass, aiohttp_client):
             patch('homeassistant.components.hassio.HassIO.'
                   'get_homeassistant_info',
                   Mock(side_effect=HassioAPIError())):
+        hass.state = CoreState.starting
         hass.loop.run_until_complete(async_setup_component(hass, 'hassio', {
             'http': {
                 'api_password': API_PASSWORD
diff --git a/tests/components/hassio/test_discovery.py b/tests/components/hassio/test_discovery.py
index 98d0835c102..c8926a1cd18 100644
--- a/tests/components/hassio/test_discovery.py
+++ b/tests/components/hassio/test_discovery.py
@@ -1,6 +1,8 @@
 """Test config flow."""
 from unittest.mock import patch, Mock
 
+from homeassistant.setup import async_setup_component
+from homeassistant.components.hassio.handler import HassioAPIError
 from homeassistant.const import EVENT_HOMEASSISTANT_START, HTTP_HEADER_HA_AUTH
 
 from tests.common import mock_coro
@@ -29,6 +31,8 @@ async def test_hassio_discovery_startup(hass, aioclient_mock, hassio_client):
             'result': 'ok', 'data': {'name': "Mosquitto Test"}
         })
 
+    assert aioclient_mock.call_count == 0
+
     with patch('homeassistant.components.mqtt.'
                'config_flow.FlowHandler.async_step_hassio',
                Mock(return_value=mock_coro({"type": "abort"}))) as mock_mqtt:
@@ -44,6 +48,55 @@ async def test_hassio_discovery_startup(hass, aioclient_mock, hassio_client):
         })
 
 
+async def test_hassio_discovery_startup_done(hass, aioclient_mock,
+                                             hassio_client):
+    """Test startup and discovery with hass discovery."""
+    aioclient_mock.get(
+        "http://127.0.0.1/discovery", json={
+            'result': 'ok', 'data': {'discovery': [
+                {
+                    "service": "mqtt", "uuid": "test",
+                    "addon": "mosquitto", "config":
+                    {
+                        'broker': 'mock-broker',
+                        'port': 1883,
+                        'username': 'mock-user',
+                        'password': 'mock-pass',
+                        'protocol': '3.1.1'
+                    }
+                }
+            ]}})
+    aioclient_mock.get(
+        "http://127.0.0.1/addons/mosquitto/info", json={
+            'result': 'ok', 'data': {'name': "Mosquitto Test"}
+        })
+
+    with patch('homeassistant.components.hassio.HassIO.update_hass_api',
+               Mock(return_value=mock_coro({"result": "ok"}))), \
+            patch('homeassistant.components.hassio.HassIO.'
+                  'get_homeassistant_info',
+                  Mock(side_effect=HassioAPIError())), \
+            patch('homeassistant.components.mqtt.'
+                  'config_flow.FlowHandler.async_step_hassio',
+                  Mock(return_value=mock_coro({"type": "abort"}))
+                  ) as mock_mqtt:
+        await hass.async_start()
+        await async_setup_component(hass, 'hassio', {
+            'http': {
+                'api_password': API_PASSWORD
+            }
+        })
+        await hass.async_block_till_done()
+
+        assert aioclient_mock.call_count == 2
+        assert mock_mqtt.called
+        mock_mqtt.assert_called_with({
+            'broker': 'mock-broker', 'port': 1883, 'username': 'mock-user',
+            'password': 'mock-pass', 'protocol': '3.1.1',
+            'addon': 'Mosquitto Test',
+        })
+
+
 async def test_hassio_discovery_webhook(hass, aioclient_mock, hassio_client):
     """Test discovery webhook."""
     aioclient_mock.get(