diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index f5e4c1a8640f45..644bbe615f7c9e 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1180,8 +1180,9 @@ are always available.  They are listed here in alphabetical order.
 
    *buffering* is an optional integer used to set the buffering policy.  Pass 0
    to switch buffering off (only allowed in binary mode), 1 to select line
-   buffering (only usable in text mode), and an integer > 1 to indicate the size
-   in bytes of a fixed-size chunk buffer. Note that specifying a buffer size this
+   buffering (only usable in text mode), an integer > 1 to indicate the size
+   in bytes of a fixed-size chunk buffer, or -1 to use the default buffering
+   policy. Note that specifying a buffer size this
    way applies for binary buffered I/O, but ``TextIOWrapper`` (i.e., files opened
    with ``mode='r+'``) would have another buffering. To disable buffering in
    ``TextIOWrapper``, consider using the ``write_through`` flag for
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 0bfdeaafae274b..9be3c873660bcf 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -122,8 +122,9 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None,
 
     buffering is an optional integer used to set the buffering policy.
     Pass 0 to switch buffering off (only allowed in binary mode), 1 to select
-    line buffering (only usable in text mode), and an integer > 1 to indicate
-    the size of a fixed-size chunk buffer.  When no buffering argument is
+    line buffering (only usable in text mode), an integer > 1 to indicate
+    the size of a fixed-size chunk buffer, or -1 to use the default buffering
+    policy. When no buffering argument is
     given, the default buffering policy works as follows:
 
     * Binary files are buffered in fixed-size chunks; the size of the buffer
diff --git a/Modules/_io/_iomodule.c b/Modules/_io/_iomodule.c
index 38ef24637b7318..f8a3fd1ed218e0 100644
--- a/Modules/_io/_iomodule.c
+++ b/Modules/_io/_iomodule.c
@@ -123,8 +123,9 @@ platform-dependent encoding or using the specified encoding if given.
 
 buffering is an optional integer used to set the buffering policy.
 Pass 0 to switch buffering off (only allowed in binary mode), 1 to select
-line buffering (only usable in text mode), and an integer > 1 to indicate
-the size of a fixed-size chunk buffer.  When no buffering argument is
+line buffering (only usable in text mode), an integer > 1 to indicate
+the size of a fixed-size chunk buffer, or -1 to use the default buffering
+policy.  When no buffering argument is
 given, the default buffering policy works as follows:
 
 * Binary files are buffered in fixed-size chunks; the size of the buffer
@@ -196,7 +197,7 @@ static PyObject *
 _io_open_impl(PyObject *module, PyObject *file, const char *mode,
               int buffering, const char *encoding, const char *errors,
               const char *newline, int closefd, PyObject *opener)
-/*[clinic end generated code: output=aefafc4ce2b46dc0 input=5bb37f174cb2fb11]*/
+/*[clinic end generated code: output=aefafc4ce2b46dc0 input=e90b1875043160db]*/
 {
     unsigned i;
 
diff --git a/Modules/_io/clinic/_iomodule.c.h b/Modules/_io/clinic/_iomodule.c.h
index 0249dd184b1d35..72bacf605a9ca0 100644
--- a/Modules/_io/clinic/_iomodule.c.h
+++ b/Modules/_io/clinic/_iomodule.c.h
@@ -53,9 +53,10 @@ PyDoc_STRVAR(_io_open__doc__,
 "\n"
 "buffering is an optional integer used to set the buffering policy.\n"
 "Pass 0 to switch buffering off (only allowed in binary mode), 1 to select\n"
-"line buffering (only usable in text mode), and an integer > 1 to indicate\n"
-"the size of a fixed-size chunk buffer.  When no buffering argument is\n"
-"given, the default buffering policy works as follows:\n"
+"line buffering (only usable in text mode), an integer > 1 to indicate\n"
+"the size of a fixed-size chunk buffer, or -1 to use the default buffering\n"
+"policy.  When no buffering argument is given, the default buffering policy\n"
+"works as follows:\n"
 "\n"
 "* Binary files are buffered in fixed-size chunks; the size of the buffer\n"
 "  is chosen using a heuristic trying to determine the underlying device\'s\n"
@@ -355,4 +356,4 @@ _io_open_code(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObjec
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=c4d7e4ef878985f8 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=262fbd17bd4cc08b input=a9049054013a1b77]*/