diff --git a/truth-table.lisp b/truth-table.lisp
index 82c45f5..496b75f 100644
--- a/truth-table.lisp
+++ b/truth-table.lisp
@@ -875,7 +875,7 @@ arguments will be placed in a list at the beginning of the alist."
 
 (defun print-usage (stream spec)
   "Print the command line usage corresponding to SPEC to STREAM."
-  (format stream "usage: truth-table [options] <proposition>~%~%")
+  (format stream "usage: truth-table [options] <propositions...>~%~%")
   (loop with longest-option
           = (apply 'max (mapcar
                          (lambda (entry)