diff --git a/openbsc/src/libmsc/gsm_04_08.c b/openbsc/src/libmsc/gsm_04_08.c
index 1e25754..8380710 100644
--- a/openbsc/src/libmsc/gsm_04_08.c
+++ b/openbsc/src/libmsc/gsm_04_08.c
@@ -3605,6 +3605,11 @@
 		return -EINVAL;
 	}
 
+	if (!conn->subscr) {
+		LOGP(DCC, LOGL_ERROR, "Invalid conn, no subscriber\n");
+		return -EINVAL;
+	}
+
 	/* Find transaction */
 	trans = trans_find_by_id(conn, GSM48_PDISC_CC, transaction_id);