diff --git a/PFERD/transform.py b/PFERD/transform.py
index 7a05dd1..a2152ba 100644
--- a/PFERD/transform.py
+++ b/PFERD/transform.py
@@ -130,7 +130,7 @@ def re_rename(regex: Regex, target: str) -> Transform:
     return inner
 
 
-def sanitize_windows_path(path: PurePath) -> Optional[PurePath]:
+def sanitize_windows_path(path: PurePath) -> PurePath:
     """
     A small function to escape characters that are forbidden in windows path names.
     This method is a no-op on other operating systems.