diff --git a/twine/repository.py b/twine/repository.py
index 5b2e288e..b512bfb3 100644
--- a/twine/repository.py
+++ b/twine/repository.py
@@ -96,8 +96,7 @@ def _convert_data_to_list_of_tuples(data: Dict[str, Any]) -> List[Tuple[str, Any
             if key in KEYWORDS_TO_NOT_FLATTEN or not isinstance(value, (list, tuple)):
                 data_to_send.append((key, value))
             else:
-                for item in value:
-                    data_to_send.append((key, item))
+                data_to_send.extend((key, item) for item in value)
         return data_to_send
 
     def set_certificate_authority(self, cacert: Optional[str]) -> None: