diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 57cdc46b86e..1343f1bc7f0 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -229,7 +229,7 @@ class DocDescriptor:
     """
     def __get__(self, obj, typ):
         return (
-            "open(file, mode='r', buffering=None, encoding=None, "
+            "open(file, mode='r', buffering=-1, encoding=None, "
                  "errors=None, newline=None, closefd=True)\n\n" +
             open.__doc__)