diff --git a/openbsc/src/libmsc/gsm_04_11.c b/openbsc/src/libmsc/gsm_04_11.c
index ba72c37..ee7f577 100644
--- a/openbsc/src/libmsc/gsm_04_11.c
+++ b/openbsc/src/libmsc/gsm_04_11.c
@@ -554,7 +554,8 @@
 {
 	uint8_t *smsp = msgb_sms(msg);
 	struct gsm_sms *gsms;
-	uint8_t sms_mti, sms_mms, sms_vpf, sms_alphabet, sms_rp;
+	unsigned int sms_alphabet;
+	uint8_t sms_mti, sms_mms, sms_vpf, sms_rp;
 	uint8_t *sms_vp;
 	uint8_t da_len_bytes;
 	uint8_t address_lv[12]; /* according to 03.40 / 9.1.2.5 */