diff --git a/stdlib/2/itertools.pyi b/stdlib/2/itertools.pyi
index 6038a67e8..487a6e5d6 100644
--- a/stdlib/2/itertools.pyi
+++ b/stdlib/2/itertools.pyi
@@ -38,7 +38,7 @@ def groupby(iterable: Iterable[_T],
             key: Callable[[_T], _S]) -> Iterator[Tuple[_S, Iterator[_T]]]: ...
 
 @overload
-def islice(iterable: Iterable[_T], stop: int) -> Iterator[_T]: ...
+def islice(iterable: Iterable[_T], stop: Optional[int]) -> Iterator[_T]: ...
 @overload
 def islice(iterable: Iterable[_T], start: Optional[int], stop: Optional[int],
            step: int = ...) -> Iterator[_T]: ...
diff --git a/stdlib/3/itertools.pyi b/stdlib/3/itertools.pyi
index 6421163ff..51a2ab374 100644
--- a/stdlib/3/itertools.pyi
+++ b/stdlib/3/itertools.pyi
@@ -40,9 +40,9 @@ def groupby(iterable: Iterable[_T],
             key: Callable[[_T], _S]) -> Iterator[Tuple[_S, Iterator[_T]]]: ...
 
 @overload
-def islice(iterable: Iterable[_T], stop: int) -> Iterator[_T]: ...
+def islice(iterable: Iterable[_T], stop: Optional[int]) -> Iterator[_T]: ...
 @overload
-def islice(iterable: Iterable[_T], start: int, stop: Optional[int],
+def islice(iterable: Iterable[_T], start: Optional[int], stop: Optional[int],
            step: int = ...) -> Iterator[_T]: ...
 
 def starmap(func: Callable[..., _S], iterable: Iterable[Iterable[Any]]) -> Iterator[_S]: ...