diff --git a/lib/vty.h b/lib/vty.h
index 3cf9c4a..ffaad35 100644
--- a/lib/vty.h
+++ b/lib/vty.h
@@ -194,7 +194,7 @@
 int vty_out (struct vty *, const char *, ...) PRINTF_ATTRIBUTE(2, 3);
 void vty_read_config (char *, char *);
 void vty_time_print (struct vty *, int);
-void vty_serv_sock (const char *, unsigned short, char *);
+void vty_serv_sock (const char *, unsigned short, const char *);
 void vty_close (struct vty *);
 char *vty_get_cwd (void);
 void vty_log (const char *, const char *, va_list);