diff --git a/python_multipart/multipart.py b/python_multipart/multipart.py
index 99a8204..bc538a3 100644
--- a/python_multipart/multipart.py
+++ b/python_multipart/multipart.py
@@ -1562,7 +1562,7 @@ def __init__(
 
             def on_start() -> None:
                 nonlocal file
-                file = FileClass(file_name, None, content_type=None, config=cast("FileConfig", self.config))
+                file = FileClass(file_name, config=cast("FileConfig", self.config))
 
             def on_data(data: bytes, start: int, end: int) -> None:
                 nonlocal file