diff --git a/vision/unit_tests/test__gax.py b/vision/unit_tests/test__gax.py
index 57ed8070a12d3..cf1172661f637 100644
--- a/vision/unit_tests/test__gax.py
+++ b/vision/unit_tests/test__gax.py
@@ -17,11 +17,6 @@
 import mock
 
 
-def _make_credentials():
-    import google.auth.credentials
-    return mock.Mock(spec=google.auth.credentials.Credentials)
-
-
 class TestGAXClient(unittest.TestCase):
     def _get_target_class(self):
         from google.cloud.vision._gax import _GAPICVisionAPI
@@ -31,13 +26,11 @@ def _make_one(self, *args, **kwargs):
         return self._get_target_class()(*args, **kwargs)
 
     def test_ctor(self):
-        from google.cloud.gapic.vision.v1 import image_annotator_client
-
-        client = mock.Mock(credentials=_make_credentials())
-        api = self._make_one(client)
+        client = mock.Mock()
+        with mock.patch('google.cloud.vision._gax.image_annotator_client.'
+                        'ImageAnnotatorClient'):
+            api = self._make_one(client)
         self.assertIs(api._client, client)
-        self.assertIsInstance(api._api,
-                              image_annotator_client.ImageAnnotatorClient)
 
 
 class TestToGAPICFeature(unittest.TestCase):
diff --git a/vision/unit_tests/test_client.py b/vision/unit_tests/test_client.py
index bd6e4791ac73b..a0d3f101c3f1c 100644
--- a/vision/unit_tests/test_client.py
+++ b/vision/unit_tests/test_client.py
@@ -59,8 +59,9 @@ def test_make_gax_client(self):
         from google.cloud.vision._gax import _GAPICVisionAPI
 
         credentials = _make_credentials()
-        client = self._make_one(project=PROJECT, credentials=credentials,
-                                use_gax=None)
+        with mock.patch('google.cloud.vision.client._GAPICVisionAPI'):
+            client = self._make_one(project=PROJECT, credentials=credentials,
+                                    use_gax=None)
         client._connection = _Connection()
         self.assertIsInstance(client._vision_api, _GAPICVisionAPI)