diff --git a/stdlib/2/__builtin__.pyi b/stdlib/2/__builtin__.pyi
index 802461a48c47..765656c19490 100644
--- a/stdlib/2/__builtin__.pyi
+++ b/stdlib/2/__builtin__.pyi
@@ -5,13 +5,16 @@ from typing import (
     TypeVar, Iterator, Iterable, NoReturn, overload, Container,
     Sequence, MutableSequence, Mapping, MutableMapping, Tuple, List, Any, Dict, Callable, Generic,
     Set, AbstractSet, FrozenSet, MutableSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsAbs,
-    SupportsComplex, IO, BinaryIO, TextIO, Union,
+    SupportsComplex, IO, BinaryIO, Union,
     ItemsView, KeysView, ValuesView, ByteString, Optional, AnyStr, Type, Text,
     Protocol,
 )
-from abc import abstractmethod, ABCMeta
+from abc import ABCMeta
 from ast import mod, AST
-from io import _OpenBinaryMode, _OpenTextMode
+from io import (
+    _OpenBinaryMode, _OpenTextMode, _OpenBinaryModeUpdating, _OpenBinaryModeWriting, _OpenBinaryModeReading,
+    TextIOWrapper, FileIO, BufferedRandom, BufferedReader, BufferedWriter
+)
 from types import TracebackType, CodeType
 import sys
 
@@ -1364,7 +1367,9 @@ if sys.version_info >= (3,):
         _OpenFile = Union[str, bytes, int, _PathLike[Any]]
     else:
         _OpenFile = Union[str, bytes, int]
+    _Opener = Callable[[str, int], int]
 
+    # Text mode: always returns a TextIOWrapper
     @overload
     def open(
         file: _OpenFile,
@@ -1374,19 +1379,71 @@ if sys.version_info >= (3,):
         errors: Optional[str] = ...,
         newline: Optional[str] = ...,
         closefd: bool = ...,
-        opener: Optional[Callable[[str, int], int]] = ...,
-    ) -> TextIO: ...
+        opener: Optional[_Opener] = ...,
+    ) -> TextIOWrapper: ...
+
+    # Unbuffered binary mode: returns a FileIO
     @overload
     def open(
         file: _OpenFile,
         mode: _OpenBinaryMode,
-        buffering: int = ...,
+        buffering: Literal[0],
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> FileIO: ...
+
+    # Buffering is on: return BufferedRandom, BufferedReader, or BufferedWriter
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryModeUpdating,
+        buffering: Literal[-1, 1] = ...,
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> BufferedRandom: ...
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryModeWriting,
+        buffering: Literal[-1, 1] = ...,
         encoding: None = ...,
         errors: None = ...,
         newline: None = ...,
         closefd: bool = ...,
-        opener: Optional[Callable[[str, int], int]] = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> BufferedWriter: ...
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryModeReading,
+        buffering: Literal[-1, 1] = ...,
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> BufferedReader: ...
+
+    # Buffering cannot be determined: fall back to BinaryIO
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryMode,
+        buffering: int,
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
     ) -> BinaryIO: ...
+
+    # Fallback if mode is not specified
     @overload
     def open(
         file: _OpenFile,
@@ -1396,7 +1453,7 @@ if sys.version_info >= (3,):
         errors: Optional[str] = ...,
         newline: Optional[str] = ...,
         closefd: bool = ...,
-        opener: Optional[Callable[[str, int], int]] = ...,
+        opener: Optional[_Opener] = ...,
     ) -> IO[Any]: ...
 
 else:
diff --git a/stdlib/2/io.pyi b/stdlib/2/io.pyi
index 0626df42778f..c4622b135b9b 100644
--- a/stdlib/2/io.pyi
+++ b/stdlib/2/io.pyi
@@ -28,12 +28,20 @@ _OpenTextMode = Literal[
     'a', 'a+', '+a', 'at', 'ta', 'at+', 'a+t', '+at', 'ta+', 't+a', '+ta',
     'U', 'rU', 'Ur', 'rtU', 'rUt', 'Urt', 'trU', 'tUr', 'Utr',
 ]
-_OpenBinaryMode = Literal[
-    'rb', 'br', 'rb+', 'r+b', '+rb', 'br+', 'b+r', '+br',
-    'wb', 'bw', 'wb+', 'w+b', '+wb', 'bw+', 'b+w', '+bw',
-    'ab', 'ba', 'ab+', 'a+b', '+ab', 'ba+', 'b+a', '+ba',
+_OpenBinaryModeUpdating = Literal[
+    'rb+', 'r+b', '+rb', 'br+', 'b+r', '+br',
+    'wb+', 'w+b', '+wb', 'bw+', 'b+w', '+bw',
+    'ab+', 'a+b', '+ab', 'ba+', 'b+a', '+ba',
+]
+_OpenBinaryModeWriting = Literal[
+    'wb', 'bw',
+    'ab', 'ba',
+]
+_OpenBinaryModeReading = Literal[
+    'rb', 'br',
     'rbU', 'rUb', 'Urb', 'brU', 'bUr', 'Ubr',
 ]
+_OpenBinaryMode = Union[_OpenBinaryModeUpdating, _OpenBinaryModeReading, _OpenBinaryModeWriting]
 
 def _OpenWrapper(file: Union[str, unicode, int],
                  mode: unicode = ..., buffering: int = ..., encoding: unicode = ...,
diff --git a/stdlib/2and3/builtins.pyi b/stdlib/2and3/builtins.pyi
index 802461a48c47..765656c19490 100644
--- a/stdlib/2and3/builtins.pyi
+++ b/stdlib/2and3/builtins.pyi
@@ -5,13 +5,16 @@ from typing import (
     TypeVar, Iterator, Iterable, NoReturn, overload, Container,
     Sequence, MutableSequence, Mapping, MutableMapping, Tuple, List, Any, Dict, Callable, Generic,
     Set, AbstractSet, FrozenSet, MutableSet, Sized, Reversible, SupportsInt, SupportsFloat, SupportsAbs,
-    SupportsComplex, IO, BinaryIO, TextIO, Union,
+    SupportsComplex, IO, BinaryIO, Union,
     ItemsView, KeysView, ValuesView, ByteString, Optional, AnyStr, Type, Text,
     Protocol,
 )
-from abc import abstractmethod, ABCMeta
+from abc import ABCMeta
 from ast import mod, AST
-from io import _OpenBinaryMode, _OpenTextMode
+from io import (
+    _OpenBinaryMode, _OpenTextMode, _OpenBinaryModeUpdating, _OpenBinaryModeWriting, _OpenBinaryModeReading,
+    TextIOWrapper, FileIO, BufferedRandom, BufferedReader, BufferedWriter
+)
 from types import TracebackType, CodeType
 import sys
 
@@ -1364,7 +1367,9 @@ if sys.version_info >= (3,):
         _OpenFile = Union[str, bytes, int, _PathLike[Any]]
     else:
         _OpenFile = Union[str, bytes, int]
+    _Opener = Callable[[str, int], int]
 
+    # Text mode: always returns a TextIOWrapper
     @overload
     def open(
         file: _OpenFile,
@@ -1374,19 +1379,71 @@ if sys.version_info >= (3,):
         errors: Optional[str] = ...,
         newline: Optional[str] = ...,
         closefd: bool = ...,
-        opener: Optional[Callable[[str, int], int]] = ...,
-    ) -> TextIO: ...
+        opener: Optional[_Opener] = ...,
+    ) -> TextIOWrapper: ...
+
+    # Unbuffered binary mode: returns a FileIO
     @overload
     def open(
         file: _OpenFile,
         mode: _OpenBinaryMode,
-        buffering: int = ...,
+        buffering: Literal[0],
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> FileIO: ...
+
+    # Buffering is on: return BufferedRandom, BufferedReader, or BufferedWriter
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryModeUpdating,
+        buffering: Literal[-1, 1] = ...,
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> BufferedRandom: ...
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryModeWriting,
+        buffering: Literal[-1, 1] = ...,
         encoding: None = ...,
         errors: None = ...,
         newline: None = ...,
         closefd: bool = ...,
-        opener: Optional[Callable[[str, int], int]] = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> BufferedWriter: ...
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryModeReading,
+        buffering: Literal[-1, 1] = ...,
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
+    ) -> BufferedReader: ...
+
+    # Buffering cannot be determined: fall back to BinaryIO
+    @overload
+    def open(
+        file: _OpenFile,
+        mode: _OpenBinaryMode,
+        buffering: int,
+        encoding: None = ...,
+        errors: None = ...,
+        newline: None = ...,
+        closefd: bool = ...,
+        opener: Optional[_Opener] = ...,
     ) -> BinaryIO: ...
+
+    # Fallback if mode is not specified
     @overload
     def open(
         file: _OpenFile,
@@ -1396,7 +1453,7 @@ if sys.version_info >= (3,):
         errors: Optional[str] = ...,
         newline: Optional[str] = ...,
         closefd: bool = ...,
-        opener: Optional[Callable[[str, int], int]] = ...,
+        opener: Optional[_Opener] = ...,
     ) -> IO[Any]: ...
 
 else:
diff --git a/stdlib/3/io.pyi b/stdlib/3/io.pyi
index 76cbce4477ce..41c484e73c98 100644
--- a/stdlib/3/io.pyi
+++ b/stdlib/3/io.pyi
@@ -29,13 +29,22 @@ _OpenTextMode = Literal[
     'x', 'x+', '+x', 'xt', 'tx', 'xt+', 'x+t', '+xt', 'tx+', 't+x', '+tx',
     'U', 'rU', 'Ur', 'rtU', 'rUt', 'Urt', 'trU', 'tUr', 'Utr',
 ]
-_OpenBinaryMode = Literal[
-    'rb', 'br', 'rb+', 'r+b', '+rb', 'br+', 'b+r', '+br',
-    'wb', 'bw', 'wb+', 'w+b', '+wb', 'bw+', 'b+w', '+bw',
-    'ab', 'ba', 'ab+', 'a+b', '+ab', 'ba+', 'b+a', '+ba',
-    'xb', 'bx', 'xb+', 'x+b', '+xb', 'bx+', 'b+x', '+bx',
+_OpenBinaryModeUpdating = Literal[
+    'rb+', 'r+b', '+rb', 'br+', 'b+r', '+br',
+    'wb+', 'w+b', '+wb', 'bw+', 'b+w', '+bw',
+    'ab+', 'a+b', '+ab', 'ba+', 'b+a', '+ba',
+    'xb+', 'x+b', '+xb', 'bx+', 'b+x', '+bx',
+]
+_OpenBinaryModeWriting = Literal[
+    'wb', 'bw',
+    'ab', 'ba',
+    'xb', 'bx',
+]
+_OpenBinaryModeReading = Literal[
+    'rb', 'br',
     'rbU', 'rUb', 'Urb', 'brU', 'bUr', 'Ubr',
 ]
+_OpenBinaryMode = Union[_OpenBinaryModeUpdating, _OpenBinaryModeReading, _OpenBinaryModeWriting]
 
 open = builtins.open