diff --git a/Modules/_io/_iomodule.c b/Modules/_io/_iomodule.c
index e70c4b7..ea727f2 100644
--- a/Modules/_io/_iomodule.c
+++ b/Modules/_io/_iomodule.c
@@ -93,140 +93,145 @@
 /*
  * The main open() function
  */
-PyDoc_STRVAR(open_doc,
-"open(file, mode='r', buffering=-1, encoding=None,\n"
-"     errors=None, newline=None, closefd=True, opener=None) -> file object\n"
-"\n"
-"Open file and return a stream.  Raise IOError upon failure.\n"
-"\n"
-"file is either a text or byte string giving the name (and the path\n"
-"if the file isn't in the current working directory) of the file to\n"
-"be opened or an integer file descriptor of the file to be\n"
-"wrapped. (If a file descriptor is given, it is closed when the\n"
-"returned I/O object is closed, unless closefd is set to False.)\n"
-"\n"
-"mode is an optional string that specifies the mode in which the file\n"
-"is opened. It defaults to 'r' which means open for reading in text\n"
-"mode.  Other common values are 'w' for writing (truncating the file if\n"
-"it already exists), 'x' for creating and writing to a new file, and\n"
-"'a' for appending (which on some Unix systems, means that all writes\n"
-"append to the end of the file regardless of the current seek position).\n"
-"In text mode, if encoding is not specified the encoding used is platform\n"
-"dependent: locale.getpreferredencoding(False) is called to get the\n"
-"current locale encoding. (For reading and writing raw bytes use binary\n"
-"mode and leave encoding unspecified.) The available modes are:\n"
-"\n"
-"========= ===============================================================\n"
-"Character Meaning\n"
-"--------- ---------------------------------------------------------------\n"
-"'r'       open for reading (default)\n"
-"'w'       open for writing, truncating the file first\n"
-"'x'       create a new file and open it for writing\n"
-"'a'       open for writing, appending to the end of the file if it exists\n"
-"'b'       binary mode\n"
-"'t'       text mode (default)\n"
-"'+'       open a disk file for updating (reading and writing)\n"
-"'U'       universal newline mode (deprecated)\n"
-"========= ===============================================================\n"
-"\n"
-"The default mode is 'rt' (open for reading text). For binary random\n"
-"access, the mode 'w+b' opens and truncates the file to 0 bytes, while\n"
-"'r+b' opens the file without truncation. The 'x' mode implies 'w' and\n"
-"raises an `FileExistsError` if the file already exists.\n"
-"\n"
-"Python distinguishes between files opened in binary and text modes,\n"
-"even when the underlying operating system doesn't. Files opened in\n"
-"binary mode (appending 'b' to the mode argument) return contents as\n"
-"bytes objects without any decoding. In text mode (the default, or when\n"
-"'t' is appended to the mode argument), the contents of the file are\n"
-"returned as strings, the bytes having been first decoded using a\n"
-"platform-dependent encoding or using the specified encoding if given.\n"
-"\n"
-"'U' mode is deprecated and will raise an exception in future versions\n"
-"of Python.  It has no effect in Python 3.  Use newline to control\n"
-"universal newlines mode.\n"
-"\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"
-"\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"
-"  \"block size\" and falling back on `io.DEFAULT_BUFFER_SIZE`.\n"
-"  On many systems, the buffer will typically be 4096 or 8192 bytes long.\n"
-"\n"
-"* \"Interactive\" text files (files for which isatty() returns True)\n"
-"  use line buffering.  Other text files use the policy described above\n"
-"  for binary files.\n"
-"\n"
-"encoding is the name of the encoding used to decode or encode the\n"
-"file. This should only be used in text mode. The default encoding is\n"
-"platform dependent, but any encoding supported by Python can be\n"
-"passed.  See the codecs module for the list of supported encodings.\n"
-"\n"
-"errors is an optional string that specifies how encoding errors are to\n"
-"be handled---this argument should not be used in binary mode. Pass\n"
-"'strict' to raise a ValueError exception if there is an encoding error\n"
-"(the default of None has the same effect), or pass 'ignore' to ignore\n"
-"errors. (Note that ignoring encoding errors can lead to data loss.)\n"
-"See the documentation for codecs.register or run 'help(codecs.Codec)'\n"
-"for a list of the permitted encoding error strings.\n"
-"\n"
-"newline controls how universal newlines works (it only applies to text\n"
-"mode). It can be None, '', '\\n', '\\r', and '\\r\\n'.  It works as\n"
-"follows:\n"
-"\n"
-"* On input, if newline is None, universal newlines mode is\n"
-"  enabled. Lines in the input can end in '\\n', '\\r', or '\\r\\n', and\n"
-"  these are translated into '\\n' before being returned to the\n"
-"  caller. If it is '', universal newline mode is enabled, but line\n"
-"  endings are returned to the caller untranslated. If it has any of\n"
-"  the other legal values, input lines are only terminated by the given\n"
-"  string, and the line ending is returned to the caller untranslated.\n"
-"\n"
-"* On output, if newline is None, any '\\n' characters written are\n"
-"  translated to the system default line separator, os.linesep. If\n"
-"  newline is '' or '\\n', no translation takes place. If newline is any\n"
-"  of the other legal values, any '\\n' characters written are translated\n"
-"  to the given string.\n"
-"\n"
-"If closefd is False, the underlying file descriptor will be kept open\n"
-"when the file is closed. This does not work when a file name is given\n"
-"and must be True in that case.\n"
-"\n"
-"A custom opener can be used by passing a callable as *opener*. The\n"
-"underlying file descriptor for the file object is then obtained by\n"
-"calling *opener* with (*file*, *flags*). *opener* must return an open\n"
-"file descriptor (passing os.open as *opener* results in functionality\n"
-"similar to passing None).\n"
-"\n"
-"open() returns a file object whose type depends on the mode, and\n"
-"through which the standard file operations such as reading and writing\n"
-"are performed. When open() is used to open a file in a text mode ('w',\n"
-"'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open\n"
-"a file in a binary mode, the returned class varies: in read binary\n"
-"mode, it returns a BufferedReader; in write binary and append binary\n"
-"modes, it returns a BufferedWriter, and in read/write mode, it returns\n"
-"a BufferedRandom.\n"
-"\n"
-"It is also possible to use a string or bytearray as a file for both\n"
-"reading and writing. For strings StringIO can be used like a file\n"
-"opened in a text mode, and for bytes a BytesIO can be used like a file\n"
-"opened in a binary mode.\n"
-    );
+/*[clinic input]
+module _io
+
+_io.open
+    file: object
+    mode: str = "r"
+    buffering: int = -1
+    encoding: str(nullable=True) = NULL
+    errors: str(nullable=True) = NULL
+    newline: str(nullable=True) = NULL
+    closefd: int(c_default="1") = True
+    opener: object = None
+
+Open file and return a stream.  Raise IOError upon failure.
+
+file is either a text or byte string giving the name (and the path
+if the file isn't in the current working directory) of the file to
+be opened or an integer file descriptor of the file to be
+wrapped. (If a file descriptor is given, it is closed when the
+returned I/O object is closed, unless closefd is set to False.)
+
+mode is an optional string that specifies the mode in which the file
+is opened. It defaults to 'r' which means open for reading in text
+mode.  Other common values are 'w' for writing (truncating the file if
+it already exists), 'x' for creating and writing to a new file, and
+'a' for appending (which on some Unix systems, means that all writes
+append to the end of the file regardless of the current seek position).
+In text mode, if encoding is not specified the encoding used is platform
+dependent: locale.getpreferredencoding(False) is called to get the
+current locale encoding. (For reading and writing raw bytes use binary
+mode and leave encoding unspecified.) The available modes are:
+
+========= ===============================================================
+Character Meaning
+--------- ---------------------------------------------------------------
+'r'       open for reading (default)
+'w'       open for writing, truncating the file first
+'x'       create a new file and open it for writing
+'a'       open for writing, appending to the end of the file if it exists
+'b'       binary mode
+'t'       text mode (default)
+'+'       open a disk file for updating (reading and writing)
+'U'       universal newline mode (deprecated)
+========= ===============================================================
+
+The default mode is 'rt' (open for reading text). For binary random
+access, the mode 'w+b' opens and truncates the file to 0 bytes, while
+'r+b' opens the file without truncation. The 'x' mode implies 'w' and
+raises an `FileExistsError` if the file already exists.
+
+Python distinguishes between files opened in binary and text modes,
+even when the underlying operating system doesn't. Files opened in
+binary mode (appending 'b' to the mode argument) return contents as
+bytes objects without any decoding. In text mode (the default, or when
+'t' is appended to the mode argument), the contents of the file are
+returned as strings, the bytes having been first decoded using a
+platform-dependent encoding or using the specified encoding if given.
+
+'U' mode is deprecated and will raise an exception in future versions
+of Python.  It has no effect in Python 3.  Use newline to control
+universal newlines mode.
+
+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
+given, the default buffering policy works as follows:
+
+* Binary files are buffered in fixed-size chunks; the size of the buffer
+  is chosen using a heuristic trying to determine the underlying device's
+  "block size" and falling back on `io.DEFAULT_BUFFER_SIZE`.
+  On many systems, the buffer will typically be 4096 or 8192 bytes long.
+
+* "Interactive" text files (files for which isatty() returns True)
+  use line buffering.  Other text files use the policy described above
+  for binary files.
+
+encoding is the name of the encoding used to decode or encode the
+file. This should only be used in text mode. The default encoding is
+platform dependent, but any encoding supported by Python can be
+passed.  See the codecs module for the list of supported encodings.
+
+errors is an optional string that specifies how encoding errors are to
+be handled---this argument should not be used in binary mode. Pass
+'strict' to raise a ValueError exception if there is an encoding error
+(the default of None has the same effect), or pass 'ignore' to ignore
+errors. (Note that ignoring encoding errors can lead to data loss.)
+See the documentation for codecs.register or run 'help(codecs.Codec)'
+for a list of the permitted encoding error strings.
+
+newline controls how universal newlines works (it only applies to text
+mode). It can be None, '', '\n', '\r', and '\r\n'.  It works as
+follows:
+
+* On input, if newline is None, universal newlines mode is
+  enabled. Lines in the input can end in '\n', '\r', or '\r\n', and
+  these are translated into '\n' before being returned to the
+  caller. If it is '', universal newline mode is enabled, but line
+  endings are returned to the caller untranslated. If it has any of
+  the other legal values, input lines are only terminated by the given
+  string, and the line ending is returned to the caller untranslated.
+
+* On output, if newline is None, any '\n' characters written are
+  translated to the system default line separator, os.linesep. If
+  newline is '' or '\n', no translation takes place. If newline is any
+  of the other legal values, any '\n' characters written are translated
+  to the given string.
+
+If closefd is False, the underlying file descriptor will be kept open
+when the file is closed. This does not work when a file name is given
+and must be True in that case.
+
+A custom opener can be used by passing a callable as *opener*. The
+underlying file descriptor for the file object is then obtained by
+calling *opener* with (*file*, *flags*). *opener* must return an open
+file descriptor (passing os.open as *opener* results in functionality
+similar to passing None).
+
+open() returns a file object whose type depends on the mode, and
+through which the standard file operations such as reading and writing
+are performed. When open() is used to open a file in a text mode ('w',
+'r', 'wt', 'rt', etc.), it returns a TextIOWrapper. When used to open
+a file in a binary mode, the returned class varies: in read binary
+mode, it returns a BufferedReader; in write binary and append binary
+modes, it returns a BufferedWriter, and in read/write mode, it returns
+a BufferedRandom.
+
+It is also possible to use a string or bytearray as a file for both
+reading and writing. For strings StringIO can be used like a file
+opened in a text mode, and for bytes a BytesIO can be used like a file
+opened in a binary mode.
+[clinic start generated code]*/
 
 static PyObject *
-io_open(PyObject *self, PyObject *args, PyObject *kwds)
+_io_open_impl(PyModuleDef *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=7615d0d746eb14d2 input=0541ce15691a82f2]*/
 {
-    char *kwlist[] = {"file", "mode", "buffering",
-                      "encoding", "errors", "newline",
-                      "closefd", "opener", NULL};
-    PyObject *file, *opener = Py_None;
-    char *mode = "r";
-    int buffering = -1, closefd = 1;
-    char *encoding = NULL, *errors = NULL, *newline = NULL;
     unsigned i;
 
     int creating = 0, reading = 0, writing = 0, appending = 0, updating = 0;
@@ -242,13 +247,6 @@
     _Py_IDENTIFIER(mode);
     _Py_IDENTIFIER(close);
 
-    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|sizzziO:open", kwlist,
-                                     &file, &mode, &buffering,
-                                     &encoding, &errors, &newline,
-                                     &closefd, &opener)) {
-        return NULL;
-    }
-
     if (!PyUnicode_Check(file) &&
 	!PyBytes_Check(file) &&
 	!PyNumber_Check(file)) {
@@ -611,8 +609,10 @@
  * Module definition
  */
 
+#include "clinic/_iomodule.c.h"
+
 static PyMethodDef module_methods[] = {
-    {"open", (PyCFunction)io_open, METH_VARARGS|METH_KEYWORDS, open_doc},
+    _IO_OPEN_METHODDEF
     {NULL, NULL}
 };