diff --git a/tests/unit/cli/docker_client_test.py b/tests/unit/cli/docker_client_test.py
index 5ccde73ad..d497495b4 100644
--- a/tests/unit/cli/docker_client_test.py
+++ b/tests/unit/cli/docker_client_test.py
@@ -16,7 +16,7 @@ class DockerClientTestCase(unittest.TestCase):
             docker_client.docker_client()
 
     def test_docker_client_with_custom_timeout(self):
-        with mock.patch.dict(os.environ):
-            os.environ['DOCKER_CLIENT_TIMEOUT'] = timeout = "300"
+        timeout = 300
+        with mock.patch('compose.cli.docker_client.HTTP_TIMEOUT', 300):
             client = docker_client.docker_client()
-        self.assertEqual(client.timeout, int(timeout))
+            self.assertEqual(client.timeout, int(timeout))