diff --git a/tests/unit/test_client.py b/tests/unit/test_client.py
index 60a2cd738..5f2d7db26 100644
--- a/tests/unit/test_client.py
+++ b/tests/unit/test_client.py
@@ -103,6 +103,7 @@ def _get_target_class():
     def _make_one(self, *args, **kwargs):
         return self._get_target_class()(*args, **kwargs)
 
+    @mock.patch("os.environ", {})
     def test_constructor_defaults(self):
         from google.cloud.bigtable.client import _CLIENT_INFO
         from google.cloud.bigtable.client import DATA_SCOPE