diff --git a/ch9344.c b/ch9344.c
index 1e37293..a16af82 100644
--- a/ch9344.c
+++ b/ch9344.c
@@ -79,7 +79,7 @@ static DEFINE_IDR(ch9344_minors);
 static DEFINE_MUTEX(ch9344_minors_lock);
 
 static void ch9344_tty_set_termios(struct tty_struct *tty,
-                                   struct ktermios *termios_old);
+                                   const struct ktermios *termios_old);
 
 static int ch9344_get_portnum(int index);
 
@@ -1597,7 +1597,7 @@ u8 cal_recv_tmt(__le32 bd)
 }
 
 static void ch9344_tty_set_termios(struct tty_struct *tty,
-                                   struct ktermios *termios_old)
+                                   const struct ktermios *termios_old)
 {
     struct ch9344 *ch9344 = tty->driver_data;
     struct ktermios *termios = &tty->termios;