diff --git a/openbsc/src/gsm_04_08.c b/openbsc/src/gsm_04_08.c
index abb6e86..eeabc0f 100644
--- a/openbsc/src/gsm_04_08.c
+++ b/openbsc/src/gsm_04_08.c
@@ -899,7 +899,7 @@
 		     bts->network->network_code, bts->location_area_code);
 
 	mid = msgb_put(msg, GSM48_MID_TMSI_LEN);
-	generate_mid_from_tmsi(mid, tmsi);
+	gsm48_generate_mid_from_tmsi(mid, tmsi);
 
 	DEBUGP(DMM, "-> LOCATION UPDATE ACCEPT\n");
 
diff --git a/openbsc/src/gsm_04_08_utils.c b/openbsc/src/gsm_04_08_utils.c
index e771ea3..c62f04d 100644
--- a/openbsc/src/gsm_04_08_utils.c
+++ b/openbsc/src/gsm_04_08_utils.c
@@ -164,6 +164,12 @@
 		return 'A' + (bcd - 0xa);
 }
 
+/* only works for numbers in ascci */
+static u_int8_t char2bcd(char c)
+{
+	return c - 0x30;
+}
+
 
 void gsm0408_generate_lai(struct gsm48_loc_area_id *lai48, u_int16_t mcc,
 			 u_int16_t mnc, u_int16_t lac)
@@ -187,7 +193,7 @@
 	lai48->lac = htons(lac);
 }
 
-int generate_mid_from_tmsi(u_int8_t *buf, u_int32_t tmsi)
+int gsm48_generate_mid_from_tmsi(u_int8_t *buf, u_int32_t tmsi)
 {
 	u_int32_t *tptr = (u_int32_t *) &buf[3];
 
@@ -199,6 +205,35 @@
 	return 7;
 }
 
+int gsm48_generate_mid_from_imsi(u_int8_t *buf, const char *imsi)
+{
+	unsigned int length = strlen(imsi), i, off = 0;
+	u_int8_t odd = (length & 0x1) == 1;
+
+	buf[0] = GSM48_IE_MOBILE_ID;
+	buf[2] = char2bcd(imsi[0]) << 4 | GSM_MI_TYPE_IMSI | (odd << 3);
+
+	/* if the length is even we will fill half of the last octet */
+	if (odd)
+		buf[1] = (length + 1) >> 1;
+	else
+		buf[1] = (length + 2) >> 1;
+
+	for (i = 1; i < buf[1]; ++i) {
+		u_int8_t lower, upper;
+
+		lower = char2bcd(imsi[++off]);
+		if (!odd && off + 1 == length)
+			upper = 0x0f;
+		else
+			upper = char2bcd(imsi[++off]) & 0x0f;
+
+		buf[2 + i] = (upper << 4) | lower;
+	}
+
+	return 2 + buf[1];
+}
+
 /* Section 9.1.8 / Table 9.9 */
 struct chreq {
 	u_int8_t val;
diff --git a/openbsc/src/paging.c b/openbsc/src/paging.c
index c79356e..fd0611a 100644
--- a/openbsc/src/paging.c
+++ b/openbsc/src/paging.c
@@ -99,7 +99,7 @@
 
 	page_group = calculate_group(request->bts, request->subscr);
 	tmsi = strtoul(request->subscr->tmsi, NULL, 10);
-	mi_len = generate_mid_from_tmsi(mi, tmsi);
+	mi_len = gsm48_generate_mid_from_tmsi(mi, tmsi);
 	rsl_paging_cmd(request->bts, page_group, mi_len, mi,
 			request->chan_type);
 }