The set types can also be called without arguments.
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 45a9afc..af5d576 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -2102,7 +2102,8 @@
 };
 
 PyDoc_STRVAR(set_doc,
-"set(iterable) -> new set object\n\
+"set() -> new empty set object\n\
+set(iterable) -> new set object\n\
 \n\
 Build an unordered collection of unique elements.");
 
@@ -2200,7 +2201,8 @@
 };
 
 PyDoc_STRVAR(frozenset_doc,
-"frozenset(iterable) -> frozenset object\n\
+"frozenset() -> empty frozenset object\n\
+frozenset(iterable) -> frozenset object\n\
 \n\
 Build an immutable unordered collection of unique elements.");