default constructor was not sticking around after USEing a vocab

extra/singleton/singleton.factor

@@ -1,9 +1,10 @@
 ! Copyright (C) 2007 Doug Coleman.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: kernel parser quotations tuples words ;
+USING: kernel parser quotations prettyprint tuples words ;
 IN: singleton
 
 : SINGLETON:
     CREATE-CLASS
     dup { } define-tuple-class
+    dup unparse create-in reset-generic
     dup construct-empty 1quotation define ; parsing