diff --git a/core/prelude-core.el b/core/prelude-core.el
index c96a8b5..525c876 100644
--- a/core/prelude-core.el
+++ b/core/prelude-core.el
@@ -550,7 +550,7 @@ This follows freedesktop standards, should work in X servers."
                              '(2 "_NET_WM_STATE_FULLSCREEN" 0))
     (error "Only X server is supported")))
 
-(defun prelude-find-user-init-file (arg)
+(defun prelude-find-user-init-file (&optional arg)
   "Edit the `prelude-user-init-file', in another window.
 With a prefix argument ARG, find the `user-init-file' instead."
   (interactive "P")