Index: /branches/working-0711/ccl/lib/dumplisp.lisp
===================================================================
--- /branches/working-0711/ccl/lib/dumplisp.lisp	(revision 13141)
+++ /branches/working-0711/ccl/lib/dumplisp.lisp	(revision 13142)
@@ -57,5 +57,6 @@
                     ;; startup code.
                     (if (and (eql (typecode o) target::subtag-instance)
-                             (typep o 'buffered-stream-mixin))
+                             (typep o 'buffered-stream-mixin)
+                             (slot-boundp o 'ioblock))
                       (let ((s (slot-value o 'ioblock)))
                         (when (and (typep s 'ioblock)