--- a/tests/mop.impure-cload.lisp
+++ b/tests/mop.impure-cload.lisp
@@ -23,7 +23,7 @@
 ;;; A distilled test case from cmucl-imp for Kevin Rosenberg's
 ;;; hyperobject.  Fix from Gerd Moellmann.
 (defclass hyperobject-class (standard-class)
-  ((user-name :initarg :user-name :type string :initform nil
+  ((user-name :initarg :user-name :type (or null string) :initform nil
 	      :accessor user-name
 	      :documentation "User name for class")))