diff --git a/drivers/media/dvb/frontends/si21xx.c b/drivers/media/dvb/frontends/si21xx.c
index d21a327..4b0c99a 100644
--- a/drivers/media/dvb/frontends/si21xx.c
+++ b/drivers/media/dvb/frontends/si21xx.c
@@ -268,7 +268,7 @@
 	return (ret != 1) ? -EREMOTEIO : 0;
 }
 
-static int si21_write(struct dvb_frontend *fe, u8 *buf, int len)
+static int si21_write(struct dvb_frontend *fe, const u8 buf[], int len)
 {
 	struct si21xx_state *state = fe->demodulator_priv;