diff --git a/tc_session.py b/tc_session.py
index 08966fb..fb451d7 100644
--- a/tc_session.py
+++ b/tc_session.py
@@ -110,7 +110,7 @@ def retry(self, retries=3, backoff_factor=0.3, status_forcelist=(500, 502, 504))
             total=retries,
             read=retries,
             connect=retries,
-            backoff_factor=backoff_factor,
+            backoff_factor=backoff_factor,  # type: ignore
             status_forcelist=status_forcelist,
         )
         # mount all https requests