diff --git a/include/osmocom/abis/ipaccess.h b/include/osmocom/abis/ipaccess.h
index 6816d87..7083ce9 100644
--- a/include/osmocom/abis/ipaccess.h
+++ b/include/osmocom/abis/ipaccess.h
@@ -104,7 +104,8 @@
 };
 
 struct hsl_unit {
-	unsigned long serno;
+	uint8_t swversion;
+	uint64_t serno;
 };
 
 #endif /* _OSMO_PROTO_IPACCESS_H */