diff --git a/src/gsm/auth_milenage.c b/src/gsm/auth_milenage.c
index 1635ac6..e180762 100644
--- a/src/gsm/auth_milenage.c
+++ b/src/gsm/auth_milenage.c
@@ -30,10 +30,14 @@
 			    const uint8_t *_rand)
 {
 	size_t res_len = sizeof(vec->res);
+	uint64_t next_sqn;
 	uint8_t sqn[6];
 	int rc;
 
-	osmo_store64be_ext(aud->u.umts.sqn, sqn, 6);
+	/* keep the incremented SQN local until gsm_milenage() succeeded. */
+	next_sqn = aud->u.umts.sqn + 1;
+
+	osmo_store64be_ext(next_sqn, sqn, 6);
 	milenage_generate(aud->u.umts.opc, aud->u.umts.amf, aud->u.umts.k,
 			  sqn, _rand,
 			  vec->autn, vec->ik, vec->ck, vec->res, &res_len);
@@ -43,7 +47,9 @@
 		return rc;
 
 	vec->auth_types = OSMO_AUTH_TYPE_UMTS | OSMO_AUTH_TYPE_GSM;
-	aud->u.umts.sqn++;
+
+	/* for storage in the caller's AUC database */
+	aud->u.umts.sqn = next_sqn;
 
 	return 0;
 }
@@ -72,7 +78,7 @@
 	if (rc < 0)
 		return rc;
 
-	aud->u.umts.sqn = 1 + (osmo_load64be_ext(sqn_out, 6) >> 16);
+	aud->u.umts.sqn = osmo_load64be_ext(sqn_out, 6) >> 16;
 
 	return milenage_gen_vec(vec, aud, _rand);
 }
diff --git a/tests/auth/milenage_test.c b/tests/auth/milenage_test.c
index 187b9ad..405da65 100644
--- a/tests/auth/milenage_test.c
+++ b/tests/auth/milenage_test.c
@@ -36,7 +36,7 @@
 		.k =   { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
 			 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f },
 		.amf = { 0x00, 0x00 },
-		.sqn = 0x22,
+		.sqn = 0x21,
 	},
 };
 
diff --git a/tests/auth/milenage_test.ok b/tests/auth/milenage_test.ok
index 20c47c6..b0eb44b 100644
--- a/tests/auth/milenage_test.ok
+++ b/tests/auth/milenage_test.ok
@@ -5,7 +5,7 @@
 RES:	e9 fc 88 cc c8 a3 53 81 
 SRES:	21 5f db 4d 
 Kc:	6d e8 16 a7 59 a4 29 12 
-AUTS success: tuple generated with SQN = 33
+AUTS success: tuple generated with SQN = 32
 MILENAGE supported: 1
 OP:	00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
 OPC:	c6 a1 3b 37 87 8f 5b 82 6f 4f 81 62 a1 c8 d8 79 
diff --git a/utils/osmo-auc-gen.c b/utils/osmo-auc-gen.c
index 6fa7cec..4e2456a 100644
--- a/utils/osmo-auc-gen.c
+++ b/utils/osmo-auc-gen.c
@@ -198,6 +198,10 @@
 			}
 			ul = strtoul(optarg, 0, 10);
 			test_aud.u.umts.sqn = ul;
+			/* Before calculating the UMTS auth vector,
+			 * osmo_auth_gen_vec() increments the SQN. SQN-1 here
+			 * to end up with the SQN the user requested. */
+			test_aud.u.umts.sqn--;
 			break;
 		case 'r':
 			rc = osmo_hexparse(optarg, _rand, sizeof(_rand));
@@ -260,16 +264,14 @@
 	else {
 		dump_auth_vec(vec);
 		if (test_aud.type == OSMO_AUTH_TYPE_UMTS)
-			/* After generating, SQN is incremented, so -1 */
-			printf("SQN:\t%" PRIu64 "\n", test_aud.u.umts.sqn - 1);
+			printf("SQN:\t%" PRIu64 "\n", test_aud.u.umts.sqn);
 	}
 
 	/* After recovering SQN.MS from AUTS, milenage_gen_vec_auts() does
-	 * aud->u.umts.sqn++, and after vector generation milenage_gen_vec()
-	 * does another ++, so to show SQN.MS we need to -2 */
+	 * aud->u.umts.sqn++, so to show SQN.MS we need to -1 */
 	if (auts_is_set)
 		printf("AUTS success: SQN.MS = %" PRIu64 "\n",
-		       test_aud.u.umts.sqn - 2);
+		       test_aud.u.umts.sqn - 1);
 
 	exit(0);
 }