diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index a7a9e47..8089df1 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -676,7 +676,7 @@
    :meth:`__index__` method that returns an integer.
 
 
-.. function:: open(file, mode='r', buffering=None, encoding=None, errors=None, newline=None, closefd=True)
+.. function:: open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True)
 
    Open *file* and return a corresponding stream.  If the file cannot be opened,
    an :exc:`IOError` is raised.