diff --git a/openbsc/include/openbsc/bsc_nat.h b/openbsc/include/openbsc/bsc_nat.h
index 1035937..c313e52 100644
--- a/openbsc/include/openbsc/bsc_nat.h
+++ b/openbsc/include/openbsc/bsc_nat.h
@@ -84,6 +84,7 @@
 
 	/* do we know anything about this BSC? */
 	int authenticated;
+	uint8_t last_rand[16];
 
 	/* the fd we use to communicate */
 	struct osmo_wqueue write_queue;