diff --git a/test/lisp/custom-tests.el b/test/lisp/custom-tests.el
index d94527b558f..07f626fd65c 100644
--- a/test/lisp/custom-tests.el
+++ b/test/lisp/custom-tests.el
@@ -147,9 +147,13 @@
                                (widget-apply field :value-to-internal origvalue)
                                "bar"))))))
 
+(defconst custom-test-admin-cus-test
+  (expand-file-name "admin/cus-test.el" source-directory))
+
 (ert-deftest check-for-wrong-custom-types ()
   :tags '(:expensive-test)
-  (load (concat installation-directory "admin/cus-test.el"))
+  (skip-unless (file-readable-p custom-test-admin-cus-test))
+  (load custom-test-admin-cus-test)
   (should (null (cus-test-opts t))))
 
 ;;; custom-tests.el ends here