Index: /trunk/source/level-1/l1-streams.lisp
===================================================================
--- /trunk/source/level-1/l1-streams.lisp	(revision 13064)
+++ /trunk/source/level-1/l1-streams.lisp	(revision 13065)
@@ -225,4 +225,6 @@
 
 (defun make-heap-ivector (element-count element-type)
+  (require-type element-count `(unsigned-byte ,(- target::nbits-in-word
+						  target::num-subtag-bits)))
   (let* ((subtag (ccl::element-type-subtype element-type)))
     (unless