diff --git a/stdlib/abc.pyi b/stdlib/abc.pyi
index 110eba24a..7b39c88ed 100644
--- a/stdlib/abc.pyi
+++ b/stdlib/abc.pyi
@@ -18,8 +18,8 @@ class ABCMeta(type):
     else:
         def __new__(mcls: type[Self], name: str, bases: tuple[type, ...], namespace: dict[str, Any], **kwargs: Any) -> Self: ...
 
-    def __instancecheck__(cls: ABCMeta, instance: Any) -> Any: ...
-    def __subclasscheck__(cls: ABCMeta, subclass: Any) -> Any: ...
+    def __instancecheck__(cls: ABCMeta, instance: Any) -> bool: ...
+    def __subclasscheck__(cls: ABCMeta, subclass: type) -> bool: ...
     def _dump_registry(cls: ABCMeta, file: SupportsWrite[str] | None = ...) -> None: ...
     def register(cls: ABCMeta, subclass: type[_T]) -> type[_T]: ...
 
diff --git a/stubs/protobuf/google/protobuf/descriptor.pyi b/stubs/protobuf/google/protobuf/descriptor.pyi
index 6b2ee31a8..fafc5f9e3 100644
--- a/stubs/protobuf/google/protobuf/descriptor.pyi
+++ b/stubs/protobuf/google/protobuf/descriptor.pyi
@@ -16,7 +16,7 @@ class Error(Exception): ...
 class TypeTransformationError(Error): ...
 
 class DescriptorMetaclass(type):
-    def __instancecheck__(self, obj): ...
+    def __instancecheck__(self, obj: Any) -> bool: ...
 
 _internal_create_key: object