diff --git a/src/mdevaluate/autosave.py b/src/mdevaluate/autosave.py
index 9666d5e..9195eef 100644
--- a/src/mdevaluate/autosave.py
+++ b/src/mdevaluate/autosave.py
@@ -142,7 +142,7 @@ def load_data(filename):
 
 
 def autosave_data(
-    nargs: int, kwargs_keys: Optional[Iterable[str]] = None, version: Optional[int] = None
+    nargs: int, kwargs_keys: Optional[Iterable[str]] = None, version: Optional[str] = None
 ) -> Callable:
     """
     Enable autosaving of results for a function.