diff --git a/homeassistant/components/mobile_app/const.py b/homeassistant/components/mobile_app/const.py
index 0b6a93a39ea4cb..318076d5fd933d 100644
--- a/homeassistant/components/mobile_app/const.py
+++ b/homeassistant/components/mobile_app/const.py
@@ -160,7 +160,7 @@
         vol.Required(ATTR_GPS_ACCURACY): cv.positive_int,
         vol.Optional(ATTR_BATTERY): cv.positive_int,
         vol.Optional(ATTR_SPEED): cv.positive_int,
-        vol.Optional(ATTR_ALTITUDE): cv.positive_int,
+        vol.Optional(ATTR_ALTITUDE): vol.Coerce(float),
         vol.Optional(ATTR_COURSE): cv.positive_int,
         vol.Optional(ATTR_VERTICAL_ACCURACY): cv.positive_int,
     }
diff --git a/tests/components/mobile_app/conftest.py b/tests/components/mobile_app/conftest.py
index 33af3c2b4a76fd..1d653b73ba3a6c 100644
--- a/tests/components/mobile_app/conftest.py
+++ b/tests/components/mobile_app/conftest.py
@@ -18,7 +18,7 @@ def registry(hass):
 
 
 @pytest.fixture
-async def create_registrations(authed_api_client):
+async def create_registrations(hass, authed_api_client):
     """Return two new registrations."""
     enc_reg = await authed_api_client.post(
         "/api/mobile_app/registrations", json=REGISTER
@@ -34,6 +34,8 @@ async def create_registrations(authed_api_client):
     assert clear_reg.status == 201
     clear_reg_json = await clear_reg.json()
 
+    await hass.async_block_till_done()
+
     return (enc_reg_json, clear_reg_json)
 
 
diff --git a/tests/components/mobile_app/test_webhook.py b/tests/components/mobile_app/test_webhook.py
index 1ea2d50d8d8208..6e8efe15dd0d2e 100644
--- a/tests/components/mobile_app/test_webhook.py
+++ b/tests/components/mobile_app/test_webhook.py
@@ -216,3 +216,23 @@ async def test_webhook_requires_encryption(webhook_client, create_registrations)
     assert "error" in webhook_json
     assert webhook_json["success"] is False
     assert webhook_json["error"]["code"] == "encryption_required"
+
+
+async def test_webhook_update_location(hass, webhook_client, create_registrations):
+    """Test that encrypted registrations only accept encrypted data."""
+    resp = await webhook_client.post(
+        "/api/webhook/{}".format(create_registrations[1]["webhook_id"]),
+        json={
+            "type": "update_location",
+            "data": {"gps": [1, 2], "gps_accuracy": 10, "altitude": -10},
+        },
+    )
+
+    assert resp.status == 200
+
+    state = hass.states.get("device_tracker.test_1_2")
+    assert state is not None
+    assert state.attributes["latitude"] == 1.0
+    assert state.attributes["longitude"] == 2.0
+    assert state.attributes["gps_accuracy"] == 10
+    assert state.attributes["altitude"] == -10