diff --git a/openbsc/src/gprs/oap.c b/openbsc/src/gprs/oap.c
index a9fee56..c7c9777 100644
--- a/openbsc/src/gprs/oap.c
+++ b/openbsc/src/gprs/oap.c
@@ -214,7 +214,7 @@
 
 	OSMO_ASSERT(data);
 
-	rc = osmo_oap_decode(data, data_len, &oap_msg);
+	rc = osmo_oap_decode(&oap_msg, data, data_len);
 	if (rc < 0) {
 		LOGP(DGPRS, LOGL_ERROR,
 		     "Decoding OAP message failed with error '%s' (%d)\n",