diff --git a/stdlib/3/io.pyi b/stdlib/3/io.pyi
index 68564e89a..47fb0d2b6 100644
--- a/stdlib/3/io.pyi
+++ b/stdlib/3/io.pyi
@@ -145,7 +145,7 @@ class TextIOBase(IOBase):
     newlines: Union[str, Tuple[str, ...], None]
     def __iter__(self) -> Iterator[str]: ...  # type: ignore
     def __next__(self) -> str: ...  # type: ignore
-    def detach(self) -> IOBase: ...
+    def detach(self) -> BinaryIO: ...
     def write(self, s: str) -> int: ...
     def writelines(self, __lines: List[str]) -> None: ...  # type: ignore
     def readline(self, size: int = ...) -> str: ...  # type: ignore
@@ -164,13 +164,15 @@ class TextIOWrapper(TextIO):
     #              -> None: ...
     def __init__(
         self,
-        buffer: IO[bytes],
+        buffer: BinaryIO,
         encoding: Optional[str] = ...,
         errors: Optional[str] = ...,
         newline: Optional[str] = ...,
         line_buffering: bool = ...,
         write_through: bool = ...
     ) -> None: ...
+    @property
+    def buffer(self) -> BinaryIO: ...
     if sys.version_info >= (3, 7):
         def reconfigure(
             self,
@@ -205,7 +207,7 @@ class TextIOWrapper(TextIO):
     def __iter__(self) -> Iterator[str]: ...
     def __next__(self) -> str: ...
     def __enter__(self) -> TextIO: ...
-    def detach(self) -> IOBase: ...
+    def detach(self) -> BinaryIO: ...
     def write(self, __text: str) -> int: ...
     def readline(self, __size: int = ...) -> str: ...
     def read(self, __size: Optional[int] = ...) -> str: ...