diff --git a/uiop/package.lisp b/uiop/package.lisp
index 1ba29ce..77ff410 100644
--- a/uiop/package.lisp
+++ b/uiop/package.lisp
@@ -734,7 +734,7 @@ UNINTERN -- Remove symbols here from PACKAGE."
   (let ((ensure-form
           `(apply 'ensure-package ',(parse-define-package-form package clauses))))
     `(progn
-       #+(or ecl gcl) (defpackage ,package (:use))
+       #+(or ecl gcl mkcl) (defpackage ,package (:use))
        (eval-when (:compile-toplevel :load-toplevel :execute)
          ,ensure-form))))