Issue #14783: Backport changes from 3.2.
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 7c4a86b..39fa740 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -3799,7 +3799,7 @@
 };
 
 PyDoc_STRVAR(string_doc,
-"str(object) -> string\n\
+"str(object='') -> string\n\
 \n\
 Return a nice string representation of the object.\n\
 If the argument is a string, the return value is the same object.");