diff --git a/pandas/util/_decorators.py b/pandas/util/_decorators.py
index f4c360f476514..fb073b1d3d039 100644
--- a/pandas/util/_decorators.py
+++ b/pandas/util/_decorators.py
@@ -267,7 +267,7 @@ def deprecate_nonkeyword_arguments(
 
     Parameters
     ----------
-    version : str
+    version : str, optional
         The version in which positional arguments will become
         keyword-only. If None, then the warning message won't
         specify any particular version.