diff --git a/stdlib/3/itertools.pyi b/stdlib/3/itertools.pyi
index ddefb5af4..aef3aac78 100644
--- a/stdlib/3/itertools.pyi
+++ b/stdlib/3/itertools.pyi
@@ -10,7 +10,7 @@ Predicate = Callable[[_T], object]
 def count(start: _N = ..., step: _N = ...) -> Iterator[_N]: ...  # more general types?
 
 class cycle(Iterator[_T], Generic[_T]):
-    def __init__(self, iterable: Iterable[_T]) -> None: ...
+    def __init__(self, __iterable: Iterable[_T]) -> None: ...
     def __next__(self) -> _T: ...
     def __iter__(self) -> Iterator[_T]: ...
 
@@ -33,21 +33,23 @@ class chain(Iterator[_T], Generic[_T]):
     def __next__(self) -> _T: ...
     def __iter__(self) -> Iterator[_T]: ...
     @staticmethod
-    def from_iterable(iterable: Iterable[Iterable[_S]]) -> Iterator[_S]: ...
+    def from_iterable(__iterable: Iterable[Iterable[_S]]) -> Iterator[_S]: ...
 
 def compress(data: Iterable[_T], selectors: Iterable[Any]) -> Iterator[_T]: ...
-def dropwhile(predicate: Predicate[_T], iterable: Iterable[_T]) -> Iterator[_T]: ...
-def filterfalse(predicate: Optional[Predicate[_T]], iterable: Iterable[_T]) -> Iterator[_T]: ...
+def dropwhile(__predicate: Predicate[_T], __iterable: Iterable[_T]) -> Iterator[_T]: ...
+def filterfalse(__predicate: Optional[Predicate[_T]], __iterable: Iterable[_T]) -> Iterator[_T]: ...
 @overload
 def groupby(iterable: Iterable[_T], key: None = ...) -> Iterator[Tuple[_T, Iterator[_T]]]: ...
 @overload
 def groupby(iterable: Iterable[_T], key: Callable[[_T], _S]) -> Iterator[Tuple[_S, Iterator[_T]]]: ...
 @overload
-def islice(iterable: Iterable[_T], stop: Optional[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: Optional[int] = ...) -> Iterator[_T]: ...
-def starmap(func: Callable[..., _S], iterable: Iterable[Iterable[Any]]) -> Iterator[_S]: ...
-def takewhile(predicate: Predicate[_T], iterable: Iterable[_T]) -> Iterator[_T]: ...
+def islice(
+    __iterable: Iterable[_T], __start: Optional[int], __stop: Optional[int], __step: Optional[int] = ...
+) -> Iterator[_T]: ...
+def starmap(__function: Callable[..., _S], __iterable: Iterable[Iterable[Any]]) -> Iterator[_S]: ...
+def takewhile(__predicate: Predicate[_T], __iterable: Iterable[_T]) -> Iterator[_T]: ...
 def tee(__iterable: Iterable[_T], __n: int = ...) -> Tuple[Iterator[_T], ...]: ...
 def zip_longest(*p: Iterable[Any], fillvalue: Any = ...) -> Iterator[Any]: ...
 
@@ -58,37 +60,37 @@ _T4 = TypeVar("_T4")
 _T5 = TypeVar("_T5")
 _T6 = TypeVar("_T6")
 @overload
-def product(iter1: Iterable[_T1]) -> Iterator[Tuple[_T1]]: ...
+def product(__iter1: Iterable[_T1]) -> Iterator[Tuple[_T1]]: ...
 @overload
-def product(iter1: Iterable[_T1], iter2: Iterable[_T2]) -> Iterator[Tuple[_T1, _T2]]: ...
+def product(__iter1: Iterable[_T1], __iter2: Iterable[_T2]) -> Iterator[Tuple[_T1, _T2]]: ...
 @overload
-def product(iter1: Iterable[_T1], iter2: Iterable[_T2], iter3: Iterable[_T3]) -> Iterator[Tuple[_T1, _T2, _T3]]: ...
+def product(__iter1: Iterable[_T1], __iter2: Iterable[_T2], __iter3: Iterable[_T3]) -> Iterator[Tuple[_T1, _T2, _T3]]: ...
 @overload
 def product(
-    iter1: Iterable[_T1], iter2: Iterable[_T2], iter3: Iterable[_T3], iter4: Iterable[_T4]
+    __iter1: Iterable[_T1], __iter2: Iterable[_T2], __iter3: Iterable[_T3], __iter4: Iterable[_T4]
 ) -> Iterator[Tuple[_T1, _T2, _T3, _T4]]: ...
 @overload
 def product(
-    iter1: Iterable[_T1], iter2: Iterable[_T2], iter3: Iterable[_T3], iter4: Iterable[_T4], iter5: Iterable[_T5]
+    __iter1: Iterable[_T1], __iter2: Iterable[_T2], __iter3: Iterable[_T3], __iter4: Iterable[_T4], __iter5: Iterable[_T5]
 ) -> Iterator[Tuple[_T1, _T2, _T3, _T4, _T5]]: ...
 @overload
 def product(
-    iter1: Iterable[_T1],
-    iter2: Iterable[_T2],
-    iter3: Iterable[_T3],
-    iter4: Iterable[_T4],
-    iter5: Iterable[_T5],
-    iter6: Iterable[_T6],
+    __iter1: Iterable[_T1],
+    __iter2: Iterable[_T2],
+    __iter3: Iterable[_T3],
+    __iter4: Iterable[_T4],
+    __iter5: Iterable[_T5],
+    __iter6: Iterable[_T6],
 ) -> Iterator[Tuple[_T1, _T2, _T3, _T4, _T5, _T6]]: ...
 @overload
 def product(
-    iter1: Iterable[Any],
-    iter2: Iterable[Any],
-    iter3: Iterable[Any],
-    iter4: Iterable[Any],
-    iter5: Iterable[Any],
-    iter6: Iterable[Any],
-    iter7: Iterable[Any],
+    __iter1: Iterable[Any],
+    __iter2: Iterable[Any],
+    __iter3: Iterable[Any],
+    __iter4: Iterable[Any],
+    __iter5: Iterable[Any],
+    __iter6: Iterable[Any],
+    __iter7: Iterable[Any],
     *iterables: Iterable[Any],
 ) -> Iterator[Tuple[Any, ...]]: ...
 @overload
diff --git a/tests/stubtest_whitelists/py36.txt b/tests/stubtest_whitelists/py36.txt
index 9f56f014c..bd8eb34d9 100644
--- a/tests/stubtest_whitelists/py36.txt
+++ b/tests/stubtest_whitelists/py36.txt
@@ -30,6 +30,7 @@ importlib.metadata
 importlib.resources
 io.StringIO.readline
 ipaddress._BaseNetwork.__init__
+itertools.accumulate
 json.loads
 mmap.ACCESS_DEFAULT
 multiprocessing.shared_memory
diff --git a/tests/stubtest_whitelists/py37.txt b/tests/stubtest_whitelists/py37.txt
index 8319eb0b5..ef7db0acd 100644
--- a/tests/stubtest_whitelists/py37.txt
+++ b/tests/stubtest_whitelists/py37.txt
@@ -36,6 +36,7 @@ http.client.HTTPSConnection.__init__
 http.server.SimpleHTTPRequestHandler.__init__
 importlib.metadata
 ipaddress._BaseNetwork.__init__
+itertools.accumulate
 json.loads
 macurl2path  # removed in 3.7
 multiprocessing.shared_memory