problem in fasl reader with characters

This library yields in an error when compiled and loaded:

;; ik-bug.sls
#!r6rs
(library (ik-bug)
  (export whitespace)
  (import (rnrs base))

  (define whitespace (apply string '(#\x3000))))
;; ik-bug.sls ends here

;; test.sps
(import (ik-bug))
;; test.sps ends here

% rm -f *.ikarus-fasl && ikarus --compile-dependencies test.sps && ikarus --r6rs-script test.sps
Serializing "./ik-bug.sls.ikarus-fasl" ...
Unhandled exception:
 Condition components:
   1. &assertion
   2. &who: integer->char
   3. &message: "integer does not have a unicode representation"
   4. &irritants: (108166990413180928)