diff --git a/stdlib/3/os/__init__.pyi b/stdlib/3/os/__init__.pyi
index 4e1674ff5..f7b3ded28 100644
--- a/stdlib/3/os/__init__.pyi
+++ b/stdlib/3/os/__init__.pyi
@@ -361,7 +361,10 @@ if sys.platform != 'win32':
 def getenv(key: Text) -> Optional[str]: ...
 @overload
 def getenv(key: Text, default: _T) -> Union[str, _T]: ...
-def getenvb(key: bytes, default: bytes = ...) -> bytes: ...
+@overload
+def getenvb(key: bytes) -> Optional[bytes]: ...
+@overload
+def getenvb(key: bytes, default: _T = ...) -> Union[bytes, _T]: ...
 def putenv(__name: Union[bytes, Text], __value: Union[bytes, Text]) -> None: ...
 def unsetenv(__name: Union[bytes, Text]) -> None: ...
 
@@ -480,7 +483,7 @@ if sys.version_info >= (3, 7):
         def __next__(self) -> DirEntry[AnyStr]: ...
         def close(self) -> None: ...
     @overload
-    def scandir() -> _ScandirIterator[str]: ...
+    def scandir(path: None = ...) -> _ScandirIterator[str]: ...
     @overload
     def scandir(path: int) -> _ScandirIterator[str]: ...
     @overload
@@ -490,12 +493,12 @@ elif sys.version_info >= (3, 6):
         def __next__(self) -> DirEntry[AnyStr]: ...
         def close(self) -> None: ...
     @overload
-    def scandir() -> _ScandirIterator[str]: ...
+    def scandir(path: None = ...) -> _ScandirIterator[str]: ...
     @overload
     def scandir(path: Union[AnyStr, PathLike[AnyStr]]) -> _ScandirIterator[AnyStr]: ...
 else:
     @overload
-    def scandir() -> Iterator[DirEntry[str]]: ...
+    def scandir(path: None = ...) -> Iterator[DirEntry[str]]: ...
     @overload
     def scandir(path: AnyStr) -> Iterator[DirEntry[AnyStr]]: ...
 def stat(path: _FdOrPathType, *, dir_fd: Optional[int] = ..., follow_symlinks: bool = ...) -> stat_result: ...