diff --git a/src/cdma-sms.c b/src/cdma-sms.c
index 108455ed..5beb8b0b 100644
--- a/src/cdma-sms.c
+++ b/src/cdma-sms.c
@@ -170,7 +170,7 @@ static void ofono_cdma_sms_process_p2p(struct ofono_cdma_sms *cdma_sms,
 }
 
 void ofono_cdma_sms_deliver_notify(struct ofono_cdma_sms *cdma_sms,
-					unsigned char *pdu, int tpdu_len)
+					const unsigned char *pdu, int tpdu_len)
 {
 	static struct cdma_sms s;