diff --git a/src/cisco_gnmi/builder.py b/src/cisco_gnmi/builder.py
index 7711db6..db1d0d6 100644
--- a/src/cisco_gnmi/builder.py
+++ b/src/cisco_gnmi/builder.py
@@ -291,7 +291,9 @@ def construct(self):
             if self.__ssl_target_name_override is None:
                 if not self.__root_certificates:
                     raise Exception("Deriving override requires root certificate!")
-                self.__ssl_target_name_override = get_cn_from_cert(self.__root_certificates)
+                self.__ssl_target_name_override = get_cn_from_cert(
+                    self.__root_certificates
+                )
                 logging.warning(
                     "Overriding SSL option from certificate could increase MITM susceptibility!"
                 )