diff --git a/homeassistant/helpers/intent.py b/homeassistant/helpers/intent.py
index 5aa53f17e7b..4357c4109eb 100644
--- a/homeassistant/helpers/intent.py
+++ b/homeassistant/helpers/intent.py
@@ -137,7 +137,8 @@ class IntentHandler:
         if self._slot_schema is None:
             self._slot_schema = vol.Schema({
                 key: SLOT_SCHEMA.extend({'value': validator})
-                for key, validator in self.slot_schema.items()})
+                for key, validator in self.slot_schema.items()},
+                                           extra=vol.ALLOW_EXTRA)
 
         return self._slot_schema(slots)
 
diff --git a/tests/components/test_snips.py b/tests/components/test_snips.py
index d9238336768..baeda2c49a8 100644
--- a/tests/components/test_snips.py
+++ b/tests/components/test_snips.py
@@ -5,6 +5,7 @@ import logging
 from homeassistant.bootstrap import async_setup_component
 from homeassistant.components.mqtt import MQTT_PUBLISH_SCHEMA
 import homeassistant.components.snips as snips
+from homeassistant.helpers.intent import (ServiceIntentHandler, async_register)
 from tests.common import (async_fire_mqtt_message, async_mock_intent,
                           async_mock_service)
 
@@ -124,6 +125,49 @@ async def test_snips_intent(hass, mqtt_mock):
     assert intent.text_input == 'turn the lights green'
 
 
+async def test_snips_service_intent(hass, mqtt_mock):
+    """Test ServiceIntentHandler via Snips."""
+    hass.states.async_set('light.kitchen', 'off')
+    calls = async_mock_service(hass, 'light', 'turn_on')
+    result = await async_setup_component(hass, "snips", {
+        "snips": {},
+    })
+    assert result
+    payload = """
+    {
+        "input": "turn the light on",
+        "intent": {
+            "intentName": "Lights",
+            "probability": 0.85
+        },
+        "siteId": "default",
+        "slots": [
+            {
+                "slotName": "name",
+                "value": {
+                    "kind": "Custom",
+                    "value": "kitchen"
+                }
+            }
+        ]
+    }
+    """
+
+    async_register(hass, ServiceIntentHandler(
+        "Lights", "light", 'turn_on', "Turned {} on"))
+
+    async_fire_mqtt_message(hass, 'hermes/intent/Lights',
+                            payload)
+    await hass.async_block_till_done()
+
+    assert len(calls) == 1
+    assert calls[0].domain == 'light'
+    assert calls[0].service == 'turn_on'
+    assert calls[0].data['entity_id'] == 'light.kitchen'
+    assert 'probability' not in calls[0].data
+    assert 'site_id' not in calls[0].data
+
+
 async def test_snips_intent_with_duration(hass, mqtt_mock):
     """Test intent with Snips duration."""
     result = await async_setup_component(hass, "snips", {
diff --git a/tests/helpers/test_intent.py b/tests/helpers/test_intent.py
index a8d37a249bc..707129ae531 100644
--- a/tests/helpers/test_intent.py
+++ b/tests/helpers/test_intent.py
@@ -1,6 +1,18 @@
 """Tests for the intent helpers."""
+
+import unittest
+import voluptuous as vol
+
 from homeassistant.core import State
-from homeassistant.helpers import intent
+from homeassistant.helpers import (intent, config_validation as cv)
+
+
+class MockIntentHandler(intent.IntentHandler):
+    """Provide a mock intent handler."""
+
+    def __init__(self, slot_schema):
+        """Initialize the mock handler."""
+        self.slot_schema = slot_schema
 
 
 def test_async_match_state():
@@ -10,3 +22,25 @@ def test_async_match_state():
 
     state = intent.async_match_state(None, 'kitch', [state1, state2])
     assert state is state1
+
+
+class TestIntentHandler(unittest.TestCase):
+    """Test the Home Assistant event helpers."""
+
+    def test_async_validate_slots(self):
+        """Test async_validate_slots of IntentHandler."""
+        handler1 = MockIntentHandler({
+            vol.Required('name'): cv.string,
+            })
+
+        self.assertRaises(vol.error.MultipleInvalid,
+                          handler1.async_validate_slots, {})
+        self.assertRaises(vol.error.MultipleInvalid,
+                          handler1.async_validate_slots, {'name': 1})
+        self.assertRaises(vol.error.MultipleInvalid,
+                          handler1.async_validate_slots, {'name': 'kitchen'})
+        handler1.async_validate_slots({'name': {'value': 'kitchen'}})
+        handler1.async_validate_slots({
+            'name': {'value': 'kitchen'},
+            'probability': {'value': '0.5'}
+            })