diff --git a/requests/models.py b/requests/models.py
index 3816e8ef..dfbea854 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -403,7 +403,7 @@ class PreparedRequest(RequestEncodingMixin, RequestHooksMixin):
                 host = self._get_idna_encoded_host(host)
             except UnicodeError:
                 raise InvalidURL('URL has an invalid label.')
-        elif host.startswith(u'*'):
+        elif host.startswith((u'*', u'.')):
             raise InvalidURL('URL has an invalid label.')
 
         # Carefully reconstruct the network location
diff --git a/tests/test_requests.py b/tests/test_requests.py
index 463e8bf4..29b3aca8 100644
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -81,6 +81,8 @@ class TestRequests:
             (InvalidSchema, 'localhost.localdomain:3128/'),
             (InvalidSchema, '10.122.1.1:3128/'),
             (InvalidURL, 'http://'),
+            (InvalidURL, 'http://*example.com'),
+            (InvalidURL, 'http://.example.com'),
         ))
     def test_invalid_url(self, exception, url):
         with pytest.raises(exception):