diff --git a/stdlib/2/_io.pyi b/stdlib/2/_io.pyi
index 3f1baab15..cc6a59712 100644
--- a/stdlib/2/_io.pyi
+++ b/stdlib/2/_io.pyi
@@ -1,6 +1,9 @@
 from typing import Any, AnyStr, BinaryIO, IO, Text, TextIO, Iterable, Iterator, List, Optional, Type, Tuple, TypeVar, Union
+from mmap import mmap
 from types import TracebackType
 
+_bytearray_like = Union[bytearray, mmap]
+
 DEFAULT_BUFFER_SIZE = ...  # type: int
 
 class BlockingIOError(IOError):
@@ -41,7 +44,7 @@ class _IOBase(BinaryIO):
 class _BufferedIOBase(_IOBase):
     def read1(self, n: int) -> bytes: ...
     def read(self, size: int = ...) -> bytes: ...
-    def readinto(self, buffer: bytearray) -> int: ...
+    def readinto(self, buffer: _bytearray_like) -> int: ...
     def write(self, s: bytes) -> int: ...
     def detach(self) -> _IOBase: ...
 
@@ -92,8 +95,8 @@ class _RawIOBase(_IOBase):
 class FileIO(_RawIOBase, BytesIO):  # type: ignore  # for __enter__
     mode = ...  # type: str
     closefd = ...  # type: bool
-    def __init__(self, file: str, mode: str = ..., closefd: bool = ...) -> None: ...
-    def readinto(self, buffer: bytearray)-> int: ...
+    def __init__(self, file: Union[str, int], mode: str = ..., closefd: bool = ...) -> None: ...
+    def readinto(self, buffer: _bytearray_like)-> int: ...
     def write(self, pbuf: str) -> int: ...
 
 class IncrementalNewlineDecoder(object):
diff --git a/stdlib/3/http/client.pyi b/stdlib/3/http/client.pyi
index 30f45d845..9cd465746 100644
--- a/stdlib/3/http/client.pyi
+++ b/stdlib/3/http/client.pyi
@@ -89,7 +89,6 @@ if sys.version_info >= (3, 5):
         def __init__(self, sock: socket, debuglevel: int = ...,
                      method: Optional[str] = ..., url: Optional[str] = ...) -> None: ...
         def read(self, amt: Optional[int] = ...) -> bytes: ...
-        def readinto(self, b: bytearray) -> int: ...
         @overload
         def getheader(self, name: str) -> Optional[str]: ...
         @overload
diff --git a/stdlib/3/io.pyi b/stdlib/3/io.pyi
index ea2752dd7..f4d60329c 100644
--- a/stdlib/3/io.pyi
+++ b/stdlib/3/io.pyi
@@ -3,10 +3,13 @@ from typing import (
 )
 import builtins
 import codecs
+from mmap import mmap
 import sys
 from types import TracebackType
 from typing import TypeVar
 
+_bytearray_like = Union[bytearray, mmap]
+
 DEFAULT_BUFFER_SIZE = ...  # type: int
 
 SEEK_SET = ...  # type: int
@@ -65,10 +68,10 @@ class RawIOBase(IOBase):
 
 class BufferedIOBase(IOBase):
     def detach(self) -> RawIOBase: ...
-    def readinto(self, b: bytearray) -> int: ...
+    def readinto(self, b: _bytearray_like) -> int: ...
     def write(self, b: Union[bytes, bytearray]) -> int: ...
     if sys.version_info >= (3, 5):
-        def readinto1(self, b: bytearray) -> int: ...
+        def readinto1(self, b: _bytearray_like) -> int: ...
     if sys.version_info >= (3, 4):
         def read(self, size: Optional[int] = ...) -> bytes: ...
         def read1(self, size: int = ...) -> bytes: ...
@@ -129,10 +132,10 @@ class BytesIO(BinaryIO):
         def closed(self) -> bool: ...
     # copied from BufferedIOBase
     def detach(self) -> RawIOBase: ...
-    def readinto(self, b: bytearray) -> int: ...
+    def readinto(self, b: _bytearray_like) -> int: ...
     def write(self, b: Union[bytes, bytearray]) -> int: ...
     if sys.version_info >= (3, 5):
-        def readinto1(self, b: bytearray) -> int: ...
+        def readinto1(self, b: _bytearray_like) -> int: ...
     if sys.version_info >= (3, 4):
         def read(self, size: Optional[int] = ...) -> bytes: ...
         def read1(self, size: int = ...) -> bytes: ...