diff --git a/stdlib/2.7/__builtin__.pyi b/stdlib/2.7/__builtin__.pyi
index 464c1e0cf..e110a1a35 100644
--- a/stdlib/2.7/__builtin__.pyi
+++ b/stdlib/2.7/__builtin__.pyi
@@ -365,7 +365,7 @@ class str(basestring, Sequence[str]):
     def __ge__(self, x: unicode) -> bool: ...
     def __mod__(self, x: Any) -> str: ...
 
-class bytearray(Sequence[int]):
+class bytearray(MutableSequence[int]):
     @overload
     def __init__(self) -> None: ...
     @overload