diff --git a/stdlib/builtins.pyi b/stdlib/builtins.pyi
index 3aa14e429..94bf8a218 100644
--- a/stdlib/builtins.pyi
+++ b/stdlib/builtins.pyi
@@ -805,7 +805,7 @@ class bytearray(MutableSequence[int], ByteString):
     def __alloc__(self) -> int: ...
 
 @final
-class memoryview(Sized, Sequence[int]):
+class memoryview(Sequence[int]):
     @property
     def format(self) -> str: ...
     @property
diff --git a/stdlib/typing.pyi b/stdlib/typing.pyi
index d17a9d08f..d03a3eabb 100644
--- a/stdlib/typing.pyi
+++ b/stdlib/typing.pyi
@@ -452,10 +452,7 @@ class Container(Protocol[_T_co]):
     def __contains__(self, __x: object) -> bool: ...
 
 @runtime_checkable
-class Collection(Iterable[_T_co], Container[_T_co], Protocol[_T_co]):
-    # Implement Sized (but don't have it as a base class).
-    @abstractmethod
-    def __len__(self) -> int: ...
+class Collection(Sized, Iterable[_T_co], Container[_T_co], Protocol[_T_co]): ...
 
 class Sequence(Collection[_T_co], Reversible[_T_co], Generic[_T_co]):
     @overload