diff --git a/include/osmocom/crypt/auth.h b/include/osmocom/crypt/auth.h
index 7064c9991..1b017c0aa 100644
--- a/include/osmocom/crypt/auth.h
+++ b/include/osmocom/crypt/auth.h
@@ -10,6 +10,7 @@
 #include <osmocom/core/utils.h>
 
 #define OSMO_A5_MAX_KEY_LEN_BYTES (128/8)
+#define OSMO_MILENAGE_IND_BITLEN_MAX 28
 
 /*! Authentication Type (GSM/UMTS) */
 enum osmo_sub_auth_type {
diff --git a/src/gsm/auth_milenage.c b/src/gsm/auth_milenage.c
index e1a1dfbaa..2ddf712bf 100644
--- a/src/gsm/auth_milenage.c
+++ b/src/gsm/auth_milenage.c
@@ -112,7 +112,7 @@ static int milenage_gen_vec(struct osmo_auth_vector *vec,
 	 * { .ind_bitlen = 0, .ind = 0, .sqn = (desired_sqn - 1) }
 	 */
 
-	if (aud->u.umts.ind_bitlen > 28)
+	if (aud->u.umts.ind_bitlen > OSMO_MILENAGE_IND_BITLEN_MAX)
 		return -2;
 
 	seq_1 = 1LL << aud->u.umts.ind_bitlen;