diff --git a/stdlib/2/__builtin__.pyi b/stdlib/2/__builtin__.pyi
index 6b1d17874..35916b872 100644
--- a/stdlib/2/__builtin__.pyi
+++ b/stdlib/2/__builtin__.pyi
@@ -292,7 +292,7 @@ class unicode(basestring, Sequence[unicode]):
     def __hash__(self) -> int: ...
 
 class str(basestring, Sequence[str]):
-    def __init__(self, object: object) -> None: ...
+    def __init__(self, object: object='') -> None: ...
     def capitalize(self) -> str: ...
     def center(self, width: int, fillchar: str = ...) -> str: ...
     def count(self, x: unicode) -> int: ...