--- lisp/vm-mime.el     2013-02-15 08:44:48 +0000
+++ lisp/vm-mime.el     2013-06-02 14:46:59 +0000
@@ -1088,7 +1088,7 @@
     (save-excursion
       (setq start (point-min))
       (while (not done)
-       (setq charset (get-text-property start 'vm-charset))
+       (setq charset (or (get-text-property start 'vm-charset) "us-ascii"))
        (setq pos (next-single-property-change start 'vm-charset))
        (or pos (setq pos (point-max) done t))
        (if charset