diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index 9e175a20e22..fc4501d0cbe 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -575,7 +575,7 @@ It can be quoted, or be inside a quoted form."
                                        " " (cadr table-etc)))
                     (cddr table-etc)))))))))
 
-(defun lisp-completion-at-point (_predicate)
+(defun lisp-completion-at-point (&optional _predicate)
   (declare (obsolete elisp-completion-at-point "25.1"))
   (elisp-completion-at-point))