diff --git a/tests/lapd/lapd_test.c b/tests/lapd/lapd_test.c
index 739f9b7..2f2a7f4 100644
--- a/tests/lapd/lapd_test.c
+++ b/tests/lapd/lapd_test.c
@@ -184,6 +184,7 @@
 	/* LAPDm requires those... */
 	pp.u.data.chan_nr = 0;
 	pp.u.data.link_id = 0;
+	pp.u.data.fn = 0;
         /* feed into the LAPDm code of libosmogsm */
         rc = lapdm_phsap_up(&pp.oph, &chan->lapdm_dcch);
 	OSMO_ASSERT(rc == 0 || rc == -EBUSY);
@@ -206,6 +207,7 @@
 	/* LAPDm requires those... */
 	pp.u.data.chan_nr = 0;
 	pp.u.data.link_id = 0;
+	pp.u.data.fn = 0;
         /* feed into the LAPDm code of libosmogsm */
         rc = lapdm_phsap_up(&pp.oph, &chan->lapdm_dcch);
 	OSMO_ASSERT(rc == 0 || rc == -EBUSY);