Consider the following code, which is a simplified version of stuff that can be found in CL-Yacc: (defstruct item x) (defstruct (sub-item (:include item) (:conc-name item-)) y) The ANSI CL spec explicitly states that this is allowed, in the description of :CONC-NAME in the description of DEFSTRUCT. However, CCL generates a warning: ;Compiler warnings for "/home/pps/jch/struct-test.lisp" : ; In an