diff --git a/stdlib/3/heapq.pyi b/stdlib/3/heapq.pyi
index 8f703c581..1b0601880 100644
--- a/stdlib/3/heapq.pyi
+++ b/stdlib/3/heapq.pyi
@@ -6,13 +6,13 @@ from typing import TypeVar, List, Iterable, Any, Callable, Optional
 
 _T = TypeVar('_T')
 
-def heappush(heap: List[_T], item: _T) -> None: ...
-def heappop(heap: List[_T]) -> _T: ...
-def heappushpop(heap: List[_T], item: _T) -> _T: ...
-def heapify(x: List[_T]) -> None: ...
-def heapreplace(heap: List[_T], item: _T) -> _T: ...
-def merge(*iterables: Iterable[_T], key: Callable[[_T], Any] = ..., reverse: bool = ...) -> Iterable[_T]: ...
+def heappush(__heap: List[_T], __item: _T) -> None: ...
+def heappop(__heap: List[_T]) -> _T: ...
+def heappushpop(__heap: List[_T], __item: _T) -> _T: ...
+def heapify(__heap: List[_T]) -> None: ...
+def heapreplace(__heap: List[_T], __item: _T) -> _T: ...
+def merge(*iterables: Iterable[_T], key: Optional[Callable[[_T], Any]] = ..., reverse: bool = ...) -> Iterable[_T]: ...
 def nlargest(n: int, iterable: Iterable[_T],
              key: Optional[Callable[[_T], Any]] = ...) -> List[_T]: ...
 def nsmallest(n: int, iterable: Iterable[_T],
-              key: Callable[[_T], Any] = ...) -> List[_T]: ...
+              key: Optional[Callable[[_T], Any]] = ...) -> List[_T]: ...