diff --git a/openbsc/src/gsm_subscriber_base.c b/openbsc/src/gsm_subscriber_base.c
index d6a179b..345544d 100644
--- a/openbsc/src/gsm_subscriber_base.c
+++ b/openbsc/src/gsm_subscriber_base.c
@@ -112,6 +112,7 @@
 	memset(s, 0, sizeof(*s));
 	llist_add_tail(&s->entry, &active_subscribers);
 	s->use_count = 1;
+	s->tmsi = GSM_RESERVED_TMSI;
 
 	INIT_LLIST_HEAD(&s->requests);