diff --git a/acme/acme/client.py b/acme/acme/client.py
index cbf424f92..61c0cb34c 100644
--- a/acme/acme/client.py
+++ b/acme/acme/client.py
@@ -20,7 +20,8 @@ from acme import messages
 logger = logging.getLogger(__name__)
 
 # Python does not validate certificates by default before version 2.7.9
-if sys.version_info < (2, 7, 9):
+# https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning
+if sys.version_info < (2, 7, 9):  # pragma: no cover
     requests.packages.urllib3.contrib.pyopenssl.inject_into_urllib3()