diff --git a/openbsc/include/openbsc/gprs_gsup_messages.h b/openbsc/include/openbsc/gprs_gsup_messages.h
index c4e9757..fe8bef5 100644
--- a/openbsc/include/openbsc/gprs_gsup_messages.h
+++ b/openbsc/include/openbsc/gprs_gsup_messages.h
@@ -22,9 +22,10 @@
 #pragma once
 
 #include <stdint.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/gsm/protocol/gsm_23_003.h>
 #include <osmocom/gsm/protocol/gsm_04_08_gprs.h>
-/* Needed for GSM_IMSI_LENGTH: */
-#include <openbsc/gsm_subscriber.h>
+#include <osmocom/crypt/auth.h>
 
 #define GPRS_GSUP_MAX_NUM_PDP_INFO		10 /* GSM 09.02 limits this to 50 */
 #define GPRS_GSUP_MAX_NUM_AUTH_INFO		5
@@ -98,7 +99,7 @@
 
 struct gprs_gsup_message {
 	enum gprs_gsup_message_type	message_type;
-	char				imsi[GSM_IMSI_LENGTH];
+	char				imsi[GSM23003_IMSI_MAX_DIGITS+2];
 	enum gsm48_gmm_cause		cause;
 	enum gprs_gsup_cancel_type	cancel_type;
 	int				pdp_info_compl;
diff --git a/openbsc/include/openbsc/gprs_sgsn.h b/openbsc/include/openbsc/gprs_sgsn.h
index 49d5407..898b7a5 100644
--- a/openbsc/include/openbsc/gprs_sgsn.h
+++ b/openbsc/include/openbsc/gprs_sgsn.h
@@ -9,11 +9,10 @@
 #include <osmocom/gsm/gsm48.h>
 
 #include <osmocom/crypt/gprs_cipher.h>
+#include <osmocom/gsm/protocol/gsm_23_003.h>
 
 #include <openbsc/gsm_data.h>
 
-#define GSM_IMSI_LENGTH 17
-#define GSM_IMEI_LENGTH 17
 #define GSM_EXTENSION_LENGTH 15
 #define GSM_APN_LENGTH 102
 
@@ -98,12 +97,12 @@
 struct sgsn_mm_ctx {
 	struct llist_head	list;
 
-	char 			imsi[GSM_IMSI_LENGTH];
+	char 			imsi[GSM23003_IMSI_MAX_DIGITS+1];
 	enum gprs_mm_state	mm_state;
 	uint32_t 		p_tmsi;
 	uint32_t 		p_tmsi_old;	/* old P-TMSI before new is confirmed */
 	uint32_t 		p_tmsi_sig;
-	char 			imei[GSM_IMEI_LENGTH];
+	char 			imei[GSM23003_IMEISV_NUM_DIGITS+1];
 	/* Opt: Software Version Numbber / TS 23.195 */
 	char 			msisdn[GSM_EXTENSION_LENGTH];
 	struct gprs_ra_id	ra;
diff --git a/openbsc/include/openbsc/gsm_subscriber.h b/openbsc/include/openbsc/gsm_subscriber.h
index 7d6c776..9df989a 100644
--- a/openbsc/include/openbsc/gsm_subscriber.h
+++ b/openbsc/include/openbsc/gsm_subscriber.h
@@ -3,9 +3,8 @@
 
 #include "gsm_data.h"
 #include <osmocom/core/linuxlist.h>
+#include <osmocom/gsm/protocol/gsm_23_003.h>
 
-#define GSM_IMEI_LENGTH 17
-#define GSM_IMSI_LENGTH 17
 #define GSM_NAME_LENGTH 160
 
 #define GSM_EXTENSION_LENGTH 15 /* MSISDN can only be 15 digits length */
@@ -32,7 +31,7 @@
 
 struct gsm_equipment {
 	long long unsigned int id;
-	char imei[GSM_IMEI_LENGTH];
+	char imei[GSM23003_IMEISV_NUM_DIGITS+1];
 	char name[GSM_NAME_LENGTH];
 
 	struct gsm48_classmark1 classmark1;
@@ -45,7 +44,7 @@
 struct gsm_subscriber {
 	struct gsm_subscriber_group *group;
 	long long unsigned int id;
-	char imsi[GSM_IMSI_LENGTH];
+	char imsi[GSM23003_IMSI_MAX_DIGITS+1];
 	uint32_t tmsi;
 	uint16_t lac;
 	char name[GSM_NAME_LENGTH];
diff --git a/openbsc/include/openbsc/ipaccess.h b/openbsc/include/openbsc/ipaccess.h
index 38151c4..82e89c2 100644
--- a/openbsc/include/openbsc/ipaccess.h
+++ b/openbsc/include/openbsc/ipaccess.h
@@ -5,13 +5,14 @@
 #include "gsm_subscriber.h"
 #include <osmocom/core/linuxlist.h>
 #include <osmocom/gsm/protocol/ipaccess.h>
+#include <osmocom/gsm/protocol/gsm_23_003.h>
 
 struct ipac_msgt_sccp_state {
 	uint8_t	src_ref[3];
 	uint8_t	dst_ref[3];
 	uint8_t trans_id;
 	uint8_t invoke_id;
-	char	imsi[GSM_IMSI_LENGTH];
+	char	imsi[GSM23003_IMSI_MAX_DIGITS+1];
 	uint8_t data[0];
 } __attribute__((packed));
 
diff --git a/openbsc/src/gprs/gprs_gsup_messages.c b/openbsc/src/gprs/gprs_gsup_messages.c
index 0b1dc9b..b3c8dab 100644
--- a/openbsc/src/gprs/gprs_gsup_messages.c
+++ b/openbsc/src/gprs/gprs_gsup_messages.c
@@ -31,6 +31,7 @@
 
 #include <osmocom/gsm/tlv.h>
 #include <osmocom/core/msgb.h>
+#include <osmocom/gsm/gsm48_ie.h>
 
 #include <stdint.h>
 
diff --git a/openbsc/src/gprs/gprs_subscriber.c b/openbsc/src/gprs/gprs_subscriber.c
index 5b0bf39..648f912 100644
--- a/openbsc/src/gprs/gprs_subscriber.c
+++ b/openbsc/src/gprs/gprs_subscriber.c
@@ -757,8 +757,9 @@
 	}
 
 	if (strcpy(subscr->equipment.imei, mmctx->imei) != 0) {
-		strncpy(subscr->equipment.imei, mmctx->imei, GSM_IMEI_LENGTH-1);
-		subscr->equipment.imei[GSM_IMEI_LENGTH-1] = 0;
+		strncpy(subscr->equipment.imei, mmctx->imei,
+			sizeof(subscr->equipment.imei)-1);
+		subscr->equipment.imei[sizeof(subscr->equipment.imei)-1] = 0;
 	}
 
 	if (subscr->lac != mmctx->ra.lac)
diff --git a/openbsc/src/gprs/gtphub_ares.c b/openbsc/src/gprs/gtphub_ares.c
index 947f2dd..667013b 100644
--- a/openbsc/src/gprs/gtphub_ares.c
+++ b/openbsc/src/gprs/gtphub_ares.c
@@ -55,7 +55,7 @@
 
 	struct gtphub *hub;
 
-	char imsi_str[GSM_IMSI_LENGTH];
+	char imsi_str[GSM23003_IMSI_MAX_DIGITS+1];
 	char apn_ni_str[GSM_APN_LENGTH];
 	char apn_oi_str[GSM_APN_LENGTH];
 	int have_3dig_mnc;
diff --git a/openbsc/src/libcommon/gsm_subscriber_base.c b/openbsc/src/libcommon/gsm_subscriber_base.c
index a455824..50f4118 100644
--- a/openbsc/src/libcommon/gsm_subscriber_base.c
+++ b/openbsc/src/libcommon/gsm_subscriber_base.c
@@ -112,7 +112,7 @@
 	if (!subscr)
 		return NULL;
 
-	strncpy(subscr->imsi, imsi, GSM_IMSI_LENGTH-1);
+	strncpy(subscr->imsi, imsi, sizeof(subscr->imsi)-1);
 	subscr->group = sgrp;
 	return subscr;
 }
diff --git a/openbsc/src/libmsc/ctrl_commands.c b/openbsc/src/libmsc/ctrl_commands.c
index 9ac39de..0d6a37c 100644
--- a/openbsc/src/libmsc/ctrl_commands.c
+++ b/openbsc/src/libmsc/ctrl_commands.c
@@ -56,7 +56,7 @@
 
 	if (!imsi || !msisdn)
 		rc = 1;
-	else if (strlen(imsi) >= GSM_IMSI_LENGTH)
+	else if (strlen(imsi) > GSM23003_IMSI_MAX_DIGITS)
 		rc = 1;
 	else if (strlen(msisdn) >= GSM_EXTENSION_LENGTH)
 		rc = 1;
diff --git a/openbsc/src/libmsc/db.c b/openbsc/src/libmsc/db.c
index a23ec89..e5017ae 100644
--- a/openbsc/src/libmsc/db.c
+++ b/openbsc/src/libmsc/db.c
@@ -34,6 +34,7 @@
 #include <openbsc/db.h>
 #include <openbsc/debug.h>
 
+#include <osmocom/gsm/protocol/gsm_23_003.h>
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/statistics.h>
 #include <osmocom/core/rate_ctr.h>
@@ -529,7 +530,7 @@
 		return NULL;
 	}
 	subscr->id = dbi_conn_sequence_last(conn, NULL);
-	strncpy(subscr->imsi, imsi, GSM_IMSI_LENGTH-1);
+	strncpy(subscr->imsi, imsi, sizeof(subscr->imsi)-1);
 	dbi_result_free(result);
 	LOGP(DDB, LOGL_INFO, "New Subscriber: ID %llu, IMSI %s\n", subscr->id, subscr->imsi);
 	db_subscriber_alloc_exten(subscr);
@@ -803,7 +804,7 @@
 	const char *string;
 	string = dbi_result_get_string(result, "imsi");
 	if (string)
-		strncpy(subscr->imsi, string, GSM_IMSI_LENGTH-1);
+		strncpy(subscr->imsi, string, sizeof(subscr->imsi)-1);
 
 	string = dbi_result_get_string(result, "tmsi");
 	if (string)
@@ -1317,7 +1318,7 @@
 	return 0;
 }
 
-int db_subscriber_assoc_imei(struct gsm_subscriber *subscriber, char imei[GSM_IMEI_LENGTH])
+int db_subscriber_assoc_imei(struct gsm_subscriber *subscriber, char imei[GSM23003_IMEISV_NUM_DIGITS])
 {
 	unsigned long long equipment_id, watch_id;
 	dbi_result result;
diff --git a/openbsc/src/osmo-bsc_nat/bsc_ussd.c b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
index e080905..2f68381 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_ussd.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_ussd.c
@@ -400,7 +400,7 @@
 	if (parsed->bssap != BSSAP_MSG_DTAP)
 		return 0;
 
-	if (strlen(con->filter_state.imsi) >= GSM_IMSI_LENGTH)
+	if (strlen(con->filter_state.imsi) > GSM23003_IMSI_MAX_DIGITS)
 		return 0;
 
 	hdr48 = bsc_unpack_dtap(parsed, msg, &len);
diff --git a/openbsc/tests/gtphub/gtphub_test.c b/openbsc/tests/gtphub/gtphub_test.c
index 8ce83c8..e24967b 100644
--- a/openbsc/tests/gtphub/gtphub_test.c
+++ b/openbsc/tests/gtphub/gtphub_test.c
@@ -388,7 +388,7 @@
 #undef MAP3
 }
 
-char resolve_ggsn_got_imsi[GSM_IMSI_LENGTH];
+char resolve_ggsn_got_imsi[GSM23003_IMSI_MAX_DIGITS+1];
 char resolve_ggsn_got_ni[GSM_APN_LENGTH];
 
 struct osmo_sockaddr resolved_ggsn_addr;