diff --git a/core/operation.lisp b/core/operation.lisp
index cd34c7f..b6659da 100644
--- a/core/operation.lisp
+++ b/core/operation.lisp
@@ -170,14 +170,13 @@
(defun print-diff (stream diff)
(dolist (item diff)
(destructuring-bind (property expected probed) item
- (declare (type symbol property)
- (type list expected probed))
+ (declare (type symbol property))
(write-str stream property #\Newline
" expected ")
- (print-list expected stream)
+ (prin1 expected stream)
(write-str stream #\Newline
" probed ")
- (print-list probed stream)
+ (prin1 probed stream)
(write-str stream #\Newline))))
(defmethod print-object ((c resource-operation-failed) stream)