diff --git a/multipart/multipart.py b/multipart/multipart.py
index 3adf9ac..21d9ac1 100644
--- a/multipart/multipart.py
+++ b/multipart/multipart.py
@@ -77,7 +77,7 @@ def __init__(self, file_name: bytes | None, field_name: bytes | None, config: Fi
             ...
 
     OnFieldCallback = Callable[[FieldProtocol], None]
-    OnFileCallback = Callable[[FieldProtocol], None]
+    OnFileCallback = Callable[[FileProtocol], None]
 
 
 # Unique missing object.