diff --git a/spelling_private_dict.txt b/spelling_private_dict.txt
index d6a10c1e9..dce824580 100644
--- a/spelling_private_dict.txt
+++ b/spelling_private_dict.txt
@@ -1,6 +1,7 @@
 KiB
 MPixel
 MiB
+MissingSchema
 Ubuntu
 admin
 api
diff --git a/src/mock_vws/_decorators.py b/src/mock_vws/_decorators.py
index 5eaf39d09..27818dacf 100644
--- a/src/mock_vws/_decorators.py
+++ b/src/mock_vws/_decorators.py
@@ -6,8 +6,9 @@
 import re
 from contextlib import ContextDecorator
 from typing import Tuple, Union
-from urllib.parse import urljoin
+from urllib.parse import urljoin, urlparse
 
+import requests
 from requests_mock.mocker import Mocker
 
 from mock_vws.database import VuforiaDatabase
@@ -45,6 +46,10 @@ def __init__(  # pylint: disable=too-many-arguments
             query_recognizes_deletion_seconds: The number of seconds after a
                 target has been deleted that the query endpoint will return a
                 500 response for on a match.
+
+        Raises:
+            ``requests.exceptions.MissingSchema``: There is no schema in a
+                given URL.
         """
         super().__init__()
         self._real_http = real_http
@@ -52,6 +57,15 @@ def __init__(  # pylint: disable=too-many-arguments
 
         self._base_vws_url = base_vws_url
         self._base_vwq_url = base_vwq_url
+        missing_scheme_error = (
+            'Invalid URL "{url}": No scheme supplied. '
+            'Perhaps you meant "https://{url}".'
+        )
+        for url in (base_vwq_url, base_vws_url):
+            result = urlparse(url)
+            if not result.scheme:
+                error = missing_scheme_error.format(url=url)
+                raise requests.exceptions.MissingSchema(error)
 
         self._mock_vws_api = MockVuforiaWebServicesAPI(
             processing_time_seconds=processing_time_seconds,
diff --git a/tests/mock_vws/test_usage.py b/tests/mock_vws/test_usage.py
index 90a1cd8e5..7fef3ec2b 100644
--- a/tests/mock_vws/test_usage.py
+++ b/tests/mock_vws/test_usage.py
@@ -10,6 +10,7 @@
 
 import pytest
 import requests
+from requests.exceptions import MissingSchema
 from requests_mock.exceptions import NoMockAddress
 
 from mock_vws import MockVWS
@@ -233,6 +234,26 @@ def test_custom_base_vwq_url(self) -> None:
             requests.post(url='https://vuforia.vwq.example.com/v1/query')
             requests.get('https://vws.vuforia.com/summary')
 
+    def test_no_scheme(self) -> None:
+        """
+        An error if raised if a URL is given with no scheme.
+        """
+        with pytest.raises(MissingSchema) as exc:
+            MockVWS(base_vws_url='vuforia.vws.example.com')
+
+        expected = (
+            'Invalid URL "vuforia.vws.example.com": No scheme supplied. '
+            'Perhaps you meant "https://vuforia.vws.example.com".'
+        )
+        assert str(exc.value) == expected
+        with pytest.raises(MissingSchema) as exc:
+            MockVWS(base_vwq_url='vuforia.vwq.example.com')
+        expected = (
+            'Invalid URL "vuforia.vwq.example.com": No scheme supplied. '
+            'Perhaps you meant "https://vuforia.vwq.example.com".'
+        )
+        assert str(exc.value) == expected
+
 
 class TestCustomQueryRecognizesDeletionSeconds:
     """