diff --git a/openbsc/tests/oap/oap_test.c b/openbsc/tests/oap/oap_test.c
index 625d8d8..339d774 100644
--- a/openbsc/tests/oap/oap_test.c
+++ b/openbsc/tests/oap/oap_test.c
@@ -168,7 +168,7 @@
 
 	/* Expect the challenge response in msg_tx */
 	OSMO_ASSERT(msg_tx);
-	OSMO_ASSERT(osmo_oap_decode(msg_tx->data, msg_tx->len, &oap_tx) == 0);
+	OSMO_ASSERT(osmo_oap_decode(&oap_tx, msg_tx->data, msg_tx->len) == 0);
 	OSMO_ASSERT(oap_tx.message_type == OAP_MSGT_CHALLENGE_RESULT);
 	OSMO_ASSERT(strcmp("e2d05b598c61d9ba",
 			   osmo_hexdump_nospc(oap_tx.xres, sizeof(oap_tx.xres)))
@@ -191,7 +191,7 @@
 	OSMO_ASSERT(oap_handle(state, msg_rx, &msg_tx) == 0);
 	OSMO_ASSERT(state->registration_failures == 1);
 	OSMO_ASSERT(msg_tx);
-	OSMO_ASSERT(osmo_oap_decode(msg_tx->data, msg_tx->len, &oap_tx) == 0);
+	OSMO_ASSERT(osmo_oap_decode(&oap_tx, msg_tx->data, msg_tx->len) == 0);
 	OSMO_ASSERT(oap_tx.message_type == OAP_MSGT_REGISTER_REQUEST);
 	OSMO_ASSERT(state->state == OAP_REQUESTED_CHALLENGE);
 	msgb_free(msg_tx);