diff --git a/lib/prototypes.h b/lib/prototypes.h
index 945da008..1e77bb2c 100644
--- a/lib/prototypes.h
+++ b/lib/prototypes.h
@@ -76,7 +76,7 @@ extern char *Basename (char *str);
 extern int chown_tree (const char *, uid_t, uid_t, gid_t, gid_t);
 
 /* chowntty.c */
-extern void chown_tty (const char *, const struct passwd *);
+extern void chown_tty (const struct passwd *);
 
 /* console.c */
 extern bool console (const char *);