diff --git a/uncompyle6/main.py b/uncompyle6/main.py
index 374980b9..ca5ff13f 100644
--- a/uncompyle6/main.py
+++ b/uncompyle6/main.py
@@ -239,7 +239,7 @@ def decompile_file(
 # FIXME: combine into an options parameter
 def main(
     in_base: str,
-    out_base: str,
+    out_base: Optional[str],
     compiled_files: list,
     source_files: list,
     outfile=None,