Index: clos.lisp
===================================================================
--- clos.lisp	(revision 12934)
+++ clos.lisp	(working copy)
@@ -379,7 +379,7 @@
             class))
   (dolist (class (class-precedence-list class))
     (when (typep class 'forward-referenced-class)
-      (return-from std-finalize-inheritance)))
+      (error 'program-error  "Class ~a is not defined" (class-name class))))
   (setf (class-slots class)
                    (funcall (if (eq (class-of class) +the-standard-class+)
                                 #'std-compute-slots