diff --git a/src/main.lisp b/src/main.lisp
--- a/src/main.lisp
+++ b/src/main.lisp
@@ -32,7 +32,7 @@
              (t (push arg (getf data mode)))))
     (unless (< 0 (length (getf data :sources)))
       (report-error "There should be at least one source"))
-    (unless (> 1 (length (getf data :target)))
+    (when (> 1 (length (getf data :target)))
       (report-error "There should be no more than one target"))
     (unless (> 1 (length (getf data :body)))
       (report-error "There should be no more than one body"))