diff --git a/stdlib/2and3/mmap.pyi b/stdlib/2and3/mmap.pyi
index 933723bdb..bf5dafe19 100644
--- a/stdlib/2and3/mmap.pyi
+++ b/stdlib/2and3/mmap.pyi
@@ -62,5 +62,6 @@ else:
     class mmap(_mmap, Sequence[bytes]):
         def rfind(self, string: bytes, start: int = ..., stop: int = ...) -> int: ...
         def __getitem__(self, index: Union[int, slice]) -> bytes: ...
+        def __getslice__(self, i: Optional[int], j: Optional[int]) -> bytes: ...
         def __delitem__(self, index: Union[int, slice]) -> None: ...
         def __setitem__(self, index: Union[int, slice], object: bytes) -> None: ...