diff --git a/include/osmocom/gsm/protocol/gsm_23_003.h b/include/osmocom/gsm/protocol/gsm_23_003.h
index be1b157..3e5c3e5 100644
--- a/include/osmocom/gsm/protocol/gsm_23_003.h
+++ b/include/osmocom/gsm/protocol/gsm_23_003.h
@@ -20,6 +20,9 @@
 #define GSM23003_MME_CODE_NUM_BYTES	1
 #define GSM23003_MME_GROUP_NUM_BYTES	2
 #define GSM23003_MTMSI_NUM_BYTES	4
+/* Chapter 3.2 */
+#define GSM23003_MSISDN_MAX_DIGITS	15 /* ITU-T Rec. E.164 6.1 */
+#define GSM23003_MSISDN_MIN_DIGITS	1
 /* Chapter 6.2.1 */
 #define GSM23003_IMEI_TAC_NUM_DIGITS	8
 #define GSM23003_IMEI_SNR_NUM_DIGITS	6