Index: /branches/working-0711/ccl/level-1/l1-clos.lisp
===================================================================
--- /branches/working-0711/ccl/level-1/l1-clos.lisp	(revision 7991)
+++ /branches/working-0711/ccl/level-1/l1-clos.lisp	(revision 7992)
@@ -2036,7 +2036,5 @@
         (values nil nil)))))
 
-(defparameter *typecheck-slots-in-optimized-make-instance* nil)
-
-
+(defparameter *typecheck-slots-in-optimized-make-instance* t)
 
 
@@ -2066,10 +2064,11 @@
                   (forms))
           (flet ((generate-type-check (form type &optional spvar)
-                   (if (null *typecheck-slots-in-optimized-make-instance*)
+                   (if (or (null *typecheck-slots-in-optimized-make-instance*)
+                           (eq form t))
                      form
                      (if spvar
                        `(if ,spvar
                          (require-type ,form ',type)
-                         (%slot-unbound-marker))
+                         ,form)
                        `(require-type ,form ',type)))))
             (dolist (slot slotds)